Download Restart Review Presentation

SECTION I
Introduction
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Introductions
• Recognition of the Review Committee
and Gemini
• Introductions
3
Overview of the Presentation
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We will start with the current status of the project including an overview of the project
schedule, summary of the opto-mechanical design, electrical design, systems design,
and the cost performance to date.
The summary of the committee report items will include an issues compliance matrix,
and address specific committee concerns.
In the project overview section we will present both the plan to the RR and the plan to
completion. A discussion of the remaining issues between Gemini and NOAO is
included.
Project management will cover the GNIRS project organization, the schedule, critical
path, remaining capital and labor costs, cost performance tracking, reporting, etc.
The new GNIRS configuration will be presented in summary to familiarize the
committee with the new instrument design. We will present examples of the
requirements flowdown process, the top level configuration, and system integration.
Risk ID and mitigation is planned for the second day and will address all risk items
previously pointed out by the committee plus additional items related to the new
design, and the plan to mitigate these risks.
Sidney Wolff will then conclude our presentations and we will adjourn for the
committee to caucus.
Overview of the Presentation
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Current status of the project
Summary of committee report items
Project overview
Project management
The new GNIRS configuration
Risk identification and mitigation plan
Conclusion
Committee Caucus
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Committee Charge
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 What is NOAO’s current cost estimate to complete GNIRS and on what
schedule?
 Is this estimate consistent with NOAO’s planned resources over the
duration of the GNIRS project?
 Have the technical issues (AURA report attached for reference)
identified by the AURA review committee been addressed adequately
to permit continuation of GNIRS?
 Does NOAO now have in place an appropriate management structure
to track, plan, and control resources to ensure that GNIRS will be
delivered on time and budget?
 Are there any approaches to designing and fabricating GNIRS that can
significantly accelerate the planned delivery, e.g., through the injection
of additional NOAO resources, outsourcing the fabrication of
components, etc.?
 Have all contractual matters involving out of scope work, definition of
work, and interfacing requirements been settled with IGPO?
GNIRS Reprogramming Addresses All Committee
Report Items
 USGP WPM meets nearly daily with PM
 All information USGP requests is provided, in the format requested
 USGP attends all weekly staff meetings, notified of all other meetings in
advance
 PM solicits USGP input frequently
 More involvement of USGP in daily GNIRS activities
 Actively soliciting IGPO input
 Responsive to IGPO concerns
 More direct communication with NOAO Director
 Between Project and USGP WPM
 Systems engineering is a critical capability
 Meets all technical requirements
 Meets original weight requirements
8
GNIRS Reprogramming Addresses
All Committee Report Items
 Clearly defined NOAO/USGP relationship
 We have a new philosophy of working
 IGPO is a customer
 Our project is open (e.g., web site)
 We have a new management structure
 Full time Project Manager who reports directly to NOAO Director
 USGP WPM reports to NOAO Director
 GNIRS has new engineering & systems team
 Engineers do the design
 Formed systems engineering team (3 scientists plus PM)
 GNIRS is a new configuration
 Optical design is essentially intact
 Repackaged or redesigned entire instrument
 Addresses all technical issues in the AURA committee report
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SECTION II
Summary of Committee Report Items
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Committee Report Identified 9 Basic Concerns
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New design addresses technical issues
Systems engineering guided the design effort
We have addressed the risk items and have a mitigation plan
We have the best engineers in the organization on the project
The project has high priority and reports directly to Sidney Wolff
The IFU and OIWFS interfaces and integration have been addressed
The instrument integration will be led by the project scientists
Project Management shortcomings have been addressed
We are confident the instrument will meet requirements
Committee Report Identified 9
Basic Concerns
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Unresolved technical issues
No rigorous requirements flow down
Lack of risk ID and mitigation plan
Capability of engineering staff
Organizational hierarchy
IFU and OIWFS integration issues
Lines of responsibility for systems integration
Project management
Overall technical capabilities of the GNIRS instrument
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Committee Report Pointed Out
5 Technical Risk Areas
 Cool down time and thermal gradients
 Optical focus, alignment, mirror finish and
baffling
 Handling frame and local handling
 OIWFS modularity and integration/test
 IFU ICD and space constraints
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Compliance Matrix
Item #
Committee Issue
1
Recommendations
Appoint a PM and a PE
Separate PM and systems engineer
Assign a Systems Engineer
Adopt more rigourous PM tools
Institute configuration control
Use ICD's
Create a systems error budget
Create a risk management plan
Change from individual to team culture
Put more emphasis on importance of engineering
Define the customer
2
3
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Management/Design
Compliance
Yes
No
Comments
x
x
x
x
x
x
x
x
x
x
x
x
Only program manager appointed
Systems engineering team
Systems engineering team
extensive control system using Access
Used for OIWFS, IFU, Gemini interfaces
plan created
implemented on GNIRS project
working on this
Gemini viewed as the customer
Risk Mitigation
Cool down time
Temperature gradients
Focus changes
Optical alignment
Mirror finish
Radiation from gaps in shields
Handling frame
OIWFS modularity and alignment
IFU space allowance and ICD
Requirements flowdown
x
x
x
x
x
x
x
x
x
x
cool down time within 4 day limit
disk modules no longer used
focus mechanism included in baseline
new plan simpler
Mirrors: 3 Al, 10 glass
handled in design
special frame no longer needed
OIWFS is mounted on a modular bench
ample space provided by new design
SDN's for every level of design created
Issues and Concerns
failed to recognize sched/bud problems
failed to recognize unresolved problems
failed to recognize issues/design shortcomings
technical capabilities of GNIRS instrument
soundness of the GNIRS design
GNIRS worth investments to build it
GNIRS will be an operational asset
x
x
x
x
x
x
x
admitted and corrected
admitted and corrected
admitted and corrected
will meet science requirements
redesigned instrument
meets a need and will be on time
multi-mode capabilites
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SECTION III
Current Status of the GNIRS Project
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Activities Chart to Restart Review
 Major milestones:
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1/18
2/10
3/9
3/15
5/25
6/21
6/1,7/2
7/20-21
Hawaii review
OIWFS ICD deficiencies identified
Durham IFU meeting
Interim review #1
Interim review #2
Baseline completed for RR
ICD reviews
Restart Review
 Major activities:
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Preliminary opto-mechanical layout
Cold motor T&E
Final configuration design
Requirements flowdown
Electrical systems design
 Restart Review preparation
Activities Chart to Restart Review
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Projected Cost Performance Through July 31, 1999
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Labor budget:
Projected thru 8/1:
Capital budget:
Projected thru 8/1:
Total under plan
$443.8K
$337.1K
$ 59.0K
$ 75.0K
$ 90.7K
Restart Review work is approximately
89% complete
 Budgeted labor dollars through RR is 76% spent
 RR budgeted non-payroll capital is 127% spent
 Performance (1/1-7/30)
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BCWS = $443.8K
(budgeted cost of work scheduled)
BCWP = $394.9K
(budgeted cost of work performed, total project to RR)
ACWP = $337.1K
(actual cost of work performed total project to RR)
CPI = 1.17
(cost performance index = BCWP/ACWP)
SPI = 0.89
(schedule performance index = BCWP/BCWS)
Project is 11% behind schedule (overall to RR)
 Critical path is 19% behind schedule (opto-mechanical design)
 Schedule to completion takes this into account
 Under-spending reflects actual costs vs average rate planning
 FTE loading very close to prediction
 Cost delta’s related to actual salary rated vs planning numbers
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Reviews Prior to Restart Review
 Virtual reviews solicited from
 Tom O’Brien, OSU
 Donald Pettie, ROE
 Bobby Ulich, Kaman Aerospace
 In-process reviews:
 March 15
 May 25
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Engineering Design will Finish
December ‘99
 Under-estimated the opto-mechanical design task
 OIWFS more complicated than anticipated
 Design is mature enough to qualify for this review
 Three in-process reviews held
 Virtual reviews solicited from individuals outside
NOAO
 Reviewed by NSF and AURA in May ‘99
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Design Status
Systems
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Done by the systems engineering team led by Jay Elias
Primary vehicle is the System Design Note (SDN)
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Major way of communicating requirements and analysis/test results
Can be initiated by any member of the GNIRS team
Not restricted to the requirements definition
Produced for every level of the design
Optical-Mechanical
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Main optical bench, bulkhead structure, and thermal/structural interfaces are on critical path of
the project
All mechanisms have been addressed and preliminary designs exist
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Optical design update is complete
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More work to do on all
Final designs will be tied to results of the drive prototyping
Only adjustments in camera lens spacing, etc., and stray light analysis remain
The preliminary mechanical design will be complete in the last quarter of this year
Electrical
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Details on specifics of connector panels and wiring remain to be defined
All major electrical interfaces are defined and specified
Includes planning for the integration of OIWFS hardware
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Design Status
• Systems Engineering and Requirements
Flowdown Activity is 95% complete
• Preliminary Opto-Mechanical Design is 81%
Complete
• Preliminary Electrical Design is 75%
Complete
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SECTION IV
Project Overview
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Outline
 WBS
 Total Project including work to RR
 Project schedule
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Plan to completion
Critical path
Capital and labor costs
Resource needs
Work Breakdown Structure (WBS)
 The WBS covers the entire project from January to Completion in June, 2000
 Main Elements:
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Management and Reporting
Systems Engineering
Mechanical
Electronics
Software
Alignment and Integration
Deliverables
Procurement
 Charge numbers are derived from the WBS
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WBS
 Chart on wall
 Accounts for activities to 6th level
 Contains summary rollups of costs of each
work element
 Main tool for tracking costs and assessing cost
performance
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Milestones
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Complete Engineering Design
Final Manuals Complete
Analysis Complete
Mechanism Drive Prototype Complete
Prefab Review
Mechanism
 Filter Wheel
 Decker Slit slide
 Slit Module
 Prism Turret
 Grating Turret
 Camera Turret
 Camera Focus
 Environmental Cover
 Acquisition Mirror
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System Software Complete
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Receive WFS Hardware
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Integration Start
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Integration Complete
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System Test Complete
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Deliverables
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Pre-Acceptance Test
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Ship to Hilo
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Final Acceptance Test
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Training
Project Schedule
 Schedule overview to completion
 Summary schedule chart
 Detail schedule on wall
 Project plan on wall
 Highlights of the Project Plan
 Plan to completion
 key milestones
 milestone chart
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Critical Path
 Engineering design
 Prototype mechanism drive testing
 Pre-Fab review
 Integration and test
 Camera turret assembly
 Acceptance Test
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Projected Labor and Capital Cost
FY99
FY00
FY01
FY02
Total MM
MD
ED
ET
ME
MT
OE
IM
P
OMT
PS
PM
PA
AA
EE
Eng
11.8
0.5
3.1
2.9
2.4
0.0
1.0
0.0
0.0
2.5
2.5
1.7
1.2
2.6
0.0
30.4
0.0
8.6
21.7
13.9
0.6
9.4
16.2
0.1
17.1
15.6
6.7
7.0
6.1
0.8
54.8
1.9
4.0
21.4
13.9
0.3
81.3
11.0
0.8
15.7
15.0
6.4
6.9
1.9
0.4
11.5
0.0
4.4
6.2
9.3
2.3
14.0
2.1
3.1
19.3
10.6
4.3
4.9
3.6
1.2
108.4
2.5
20.1
52.2
39.4
3.2
105.7
29.3
4.0
54.7
43.8
19.2
20.0
14.1
2.4
Total
32.2
154.1
235.7
96.8
518.9
$178.9
$855.2
$1,307.5
$537.2
$2,878.8
$75.0
$41.4
$283.7
$9.0
Labor Cost
38 Capital
Labor ($K) Capital ($K)
$601.6
$13.7
$111.6
$289.6
$218.6
$17.7
$586.6
$162.3
$22.2
$303.6
$242.7
$106.3
$110.7
$78.5
$13.1
$2,878.8
$409.1
Capital and Labor Cost
 Cost to complete is $3.9 million
 Includes expenditures from January 1, 1999
 Labor cost to Restart Review was $443.8K and
capital cost was $75K.
 Labor cost to go is $2.88 million for 519 man months
 Capital cost to go is $409K, including outsourcing of
fabrication items
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Sufficient Key Resources are
Committed to do this Project
 Facilities are available and designated for this project effort
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Shop
Lab space
Cleanroom
Test dewar
Equipment
 ME’s, MD’s, IM’s are key resources to complete design and
fabrication
 PS(s) will be involved in and supervise integration and test
 PS(s) form systems engineering team to monitor all technical
activities
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Strategy Based on New
Design with Proven Concepts
 No new development
 Design for ease of fabrication/assembly/test
 Fabrication strategy
 In-house IM’s used primarily for mechanism fabrication
and assembly with conventional machining
 Out-sourcing to vendors where cost effective
 Castings are planned for several large assemblies
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SECTION V
Project Management
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Outline
•
•
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•
•
•
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Project organization
Management methods
Reporting
Reviews planned
Configuration control
Customer relations
The Project Reports Directly to Sidney Wolff
 Lines of authority and responsibility
 All project functions report to the Project Manager
 Mechanical design is under mechanical engineering
 Systems engineering has technical prerogative
 GNIRS Project Staff
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Project Manager
Project Scientists
Mechanical Engineers
Electrical Engineers
Optical Engineer
Mechanical Designers
Mechanical Tech
Electrical TechKen Don
Programmer
Instrument Maker
Project Assistant
Administrative Assistant
Neil Gaughan
Jay Elias/Brooke Gregory/Dick Joyce
Larry Goble/Gary Muller
Andy Rudeen
Ming Liang
John Andrew/Dave Rosin/Eric Downey
Al Davis
Richard Wolff
4 assigned
Dan Eklund
Melissa Bowersock
 Draw on other ETS resources as required
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The Project Reports Directly
to Sidney Wolff
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Project Management will Employ
Standard CSCS Methods
 Project progress status will be assessed weekly
 Allows early identification of problems for critical item tracking
 Weekly project meetings
 Cost data will be gathered bi-weekly from NOAO Accounting System
 Cost tracking will be done to the 5th and 6th level, as applicable
 Charge numbers used on the project reflect the WBS
 Cost/performance report types generated
 Accounting system generates custom reports of both labor dollars and
hours, and capital
 Summary progress report generated by PM
 Report to USGP monthly showing cost status
 MS Project standard performance reports
 Vendor management and progress tracking
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Monthly Budget Labor & Capital ($K) to Restart Review
J
F
M
A
M
J
J
CUM's
Labor Costs ($K):
Planned Labor
Actual Labor
CUM Over/Under
58.3
65.4
7.1
58.3
46.5
-4.6
56.9
43.9
-17.6
66.6
37.5
-46.6
69.4
47.3
-68.7
69.4
46.5
-91.5
65.2
443.8
287.1
-91.5
FTE Loading (FTE)
Planned
Actual
10.5
12.5
10.5
9.3
9.8
8.9
10.5
9.7
10.5
9.7
10.5
10.7
10.5
72.8
60.8
Capital ($K)
Planned Capital
Actual Capital
11.0
10.5
10.0
7.7
5.0
40.6
5.0
0.3
8.0
10.8
10.0
2.9
10.0
59.0
72.8
April labor is for first portion of the month only.
Explanations:
March:
FTE: Ilness's accounted for lower numbers for March
Capital:
filter order 29.8K
contract labor
7.0K
cold motors2.9K
misc
0.15K
April
FTE: CAS data shows a low number
Capital:
contract labor
2.6K
software
0.76K
electronics 0.69K
material
misc material
0.28K
credit
3.84K
May
FTE: Contract designer joins staff full time
Capital:
travel
7.1K
contract labor
2.9K
electronics 0.52K
material
misc
0.1K
June
FTE
Project scheduler added to staff
cold motors1.76K
misc
0.9K
Staff FTE's
ME
ME
EE
ET
MD
MD
MD
MD
IM
Psced
AA
PM
Total FTE
10.65
Goble
Muller
Rudeen
Don
Andrew
Downey
Rosin
Davis
Rath
Eklund
Bowersock
Gaughan
Scientists
PS
Elias
PS
Joyce
PS (CTIO) Gregory
80%
10%
75%
100%
50%
4 mo
GNIRS Project Monthly Status
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GNIRS Project as of June 30, 1999
Budget
Actual
Delta
Cum Plan
Cum Actual
Cum Delta
Total
this Month
this Month
this Month
to Date
to Date
to Date
Budget
Manpower
$69,350 $
46,500 $
22,850 $ 378,651 $
287,140 $
91,511 $ 2,981,495
Capital
$ 10,000 $
2,900 $
7,100 $ 59,000 $
72,797 $
(13,797) $
860,000
Total $ 79,350 $
49,400 $
29,950 $ 437,651 $
359,937 $
77,714 $ 3,841,495
Previous
Cum
to Dec 1998
$ 1,629,705
$ 748,851
$ 2,378,556
Reporting is done Monthly to
Gemini and Bi-Weekly to NOAO
 Written report
 Cost status report to Gemini
 Compares actuals to budget both monthly and
cum
 Bi-weekly reports to Sidney Wolff
 Designed to give project status to Director
 Reports financial and progress performance
 Bi-weekly report example in Appendix A
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Reviews
 Gemini review participation
 All formal reviews given to Gemini as the Customer
 Gemini is encouraged to attend and participate in all reviews
 Web reviews
 Our design will be placed on the GNIRS web site as it matures
 Review and comments are always welcome
 GNIRS is publicly accessible <http://www.noao.edu/ets/gnirs>
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Formal and Informal Reviews
are Planned
 Pre-Fabrication review
 Formal review at completion of prototyping and
engineering design
 Design will be frozen at this point and placed under
configuration control
 Mid-Fabrication review to assess schedule
performance
 Held approximately one year after fabrication start
 Internal reviews will be held as required
 Informal to assess readiness for fabrication,
procurement, etc.
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Configuration Control is Already
Implemented on the Project
 Example is on the table
 Provides for complete tracking of all assemblies
 Contained in an Access Data Base
 Managed by Gary Muller, Sr. Mechanical
Engineer responsible for design and fabrication
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Customer Relations
 Improved NOAO/USGP relationship
 USGP WPM meets nearly daily with PM
 All information USGP requests is provided, in the format
requested
 USGP attends all weekly staff meetings, notified of all other
meetings in advance
 PM solicits USGP input frequently
 More involvement of USGP in daily GNIRS activities
 IGPO is viewed as the customer
 Actively soliciting IGPO input
 Responsive to IGPO concerns
 Our project is open (e.g., web site)
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Section VI
GNIRS Configuration
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GNIRS is a New Configuration
• Requirements (Elias)
• Top Level Configuration (Elias)
• Detailed Configuration
(Gregory,Muller,Goble,Elias, Rudeen)
• Sub-System Integration (Elias)
• System Integration and Test (Elias)
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Requirements were analyzed and documented (1)
• System Design Notes (SDNs):
The System Design Notes serve several purposes. First of all, they provide a written
definition and discussion of requirements. Second, they provide a discussion of the
flow down of the requirements to individual sub-systems within the instrument. This
discussion of allocations is critical to a sensible design. Third, they may provide a
discussion of design trade-offs required to achieve required performance. This can in
principle lead to a re-allocation of requirements.
• Interface Control Documents (ICDs):
The Interface Control Documents define interfaces between external (Gemini telescope)
systems and GNIRS, and between IGPO-supplied subsystems (OIWFS, IFU, array
controller) and GNIRS. Except for the IFU, the interfaces are common to more than
one instrument, and GNIRS must conform to the ICD. The IFU is unique to GNIRS so
the interface definition is more of a joint effort.
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Requirements were analyzed
and documented (1)
• Role of SDNs:
 Define requirements
 Flow-down of requirements
 Analysis of design trade-offs
• Role of ICDs
 Define interfaces to external Gemini systems
 Define interfaces to IGPO-supplied sub-systems
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Requirements were analyzed and documented (2)
• Requirement Flow-Down:
The design notes include summaries of the requirements and an allocations to subsystems. The flow-down chart illustrates this.
What is particularly important is that the requirements, as they flow down to individual subsystems, are taken seriously by the engineering team. Thus, the approach to designing
mechanisms is to design each within a weight budget rather than charging a “weight
czar” to find out afterward whether the budget has been met. The design note
approach permits feedback from the engineers in defining the allocations, and helps
ensure that they “sign on” to the requirements.
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Requirements were analyzed
and documented (2)
• Requirements Flow-Down:
 Formal allocation of requirements
 Engineering team understands requirements and
implements them in design
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Key Science Requirements (1)
• Optical Performance
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Image Quality: several requirements, can be simplified as design image quality of 85%
of light in 1 pixel with fabrication and assembly tolerances producing less than 5%
degradation of delivered image.
Throughput: to be maximized, expectations >40%.
Excess Background: light leaks and other excess thermal emission to be less than
detector dark current.
Scattered light: scattered light to be less than detector dark for short wavelengths
(scattered light from night sky airglow).
• Flexure
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Flexure between OIWFS and spectrograph slit to be <12 microns (at slit) in 1 hour (5%
light loss with narrow slit)
Flexure between spectrograph slit and detector to be <2.7 microns (at detector) in 1
hour (0.1 pixel)
Shift of telescope secondary image on cold stop to be 1% of diameter maximum
Should include effects of thermal variations as well as gravity
• Repeatability
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Repeatability during acquisition < 0.1 pixel
Repeatability between configurations <10 pixels
Key Science Requirements (1)
• Optical Performance
• Flexure
• Repeatability
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Key Science Requirements (2)
 Cool-Down and Warm-Up
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Cool-down to take place in 4 days or less (96 hours).
Warm up to take place in 1 day or less (24 hours).
 Weight and Center of Gravity



Instrument weight = 2000 kg (ballast if necessary)
Instrument center of gravity located 1000 mm from ISS face, on optical axis
Allowable error in moment is 400 N-m relative to telescope elevation axis.
 Supports On-Instrument Wave-Front Sensor




Provides near-IR guiding on stars within 3 arcmin field (excluding those in
spectrograph slit and acquisition field)
Minimizes flexure effects (ISS, instrument and bench support)
Parallel “instrument” within GNIRS: optical system, detector/controller, 3 mechanisms
(4 axes)
Provided as sub-system by IfA (Hawaii) through IGPO
 Support of Multiple Observing Modes

70
Detailed below
Key Science Requirements (2)
•
•
•
•
71
Cool-Down and Warm-Up
Weight and Center of Gravity
Supports OIWFS
Support of Multiple Observing Modes
Several Observing Modes Supported
•
•
•
•
•
•
72
2 spatial scales: 0.05 arcsec/pixel for match to AO and best seeing; 0.15 arcsec/pixel for
more routine non-AO conditions (also gives longer slit coverage, more IFU coverage)
3 spectral resolutions: R~1800 for full coverage of atmospheric “window”; R= 5400/6000 for
observations between OH airglow lines and general higher resolution; R= 18,000 (0.05
arcsec pixels only) for highest spectral resolution.
Prism dispersers: spectral cross-dispersion for complete 0.9-2.4 micron spectra at both pixel
scales; Wollaston prism for polarization analysis (used at both scales).
Integral Field Unit (IFU): maps rectangular area onto virtual slit. Two units provide two
scales (slightly less than equivalent long-slit modes). Works with all gratings; good
performance required to 2.5 microns, desired to longer wavelengths. Provided as subsystem by U Durham through IGPO.
Acquisition mode (“flip-in” mirror) allows direct, non-dispersed viewing through slit to identify
and position objects. Does not require movement of dispersing elements.
Diagnostic modes. Intended to aid in test or diagnosis of instrument. Pupil viewing
(alignment of secondary with cold stop). Focus masks (accurate focus of detector on slit).
Several Observing Modes
Supported
•
•
•
•
•
•
73
2 Spatial Scales
3 Spectral Resolutions
Cross-Dispersion and Polarization Analysis
Integral Field Unit
Acquisition
Diagnostics
Top Level Configuration - External View
•
•
•
•
•
74
Illustrates concept (details of dewar design will conform to internal structure).
Truss structure interfaces to telescope; controls flexure, responds to thermal
variations
Additional trusses support instrument for handling, attach electronics to main
structure. Interfaces to Gemini handling equipment are part of these trusses.
Design leads to minimal complexity in dewar shell
Central bulkhead contains all interfaces to innards: cooling system, structural
(bench support), electrical
Top Level Configuration - External View
75
Top Level Configuration - Internal View
•
•
•
•
•
76
Illustrates layout of mechanical assemblies.
The design permits use of NIRI layout for OIWFS (2 folds removed). Key
elements of OIWFS identified: field lens, combination lens group
(collimator/camera), gimbal mirror (field selection), filter wheel, combination
Shack-Hartmann optics group and detector mount (“detector group”)
The design minimizes folds in spectrograph. Key elements identified: fore-optics
(spectrograph pick-off mirror, Offner relay and folds, filters, slit/decker),
collimator, prism turret, grating turret, camera turret assembly (cameras, focus,
detector)
The design permits use of acquisition (“flip”) mirror (intercepts light from
collimator and directs to camera). Minimizes motion requirements on disperser
turrets.
Central location for most large assemblies simplifies structural and thermal
design.
Internal Mechanical Configuration
OIWFS Detector group
Focal plane # 3
OIWFS Filter
wheel
Lens group
Gimbal
mirror
Collimator
Grating turret
OIWFS
field lens
Slit slide
IFU’s, Focal
plane # 2
Pick off, Focal
plane # 1
Long cam fold flats
Entrance
Window
Camera turret
Prism turret
Offner relay
Decker slide
Filter wheels
77
Detector, Focal
plane # 4
Flip mirror
not shown
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78
Detailed Configuration
• Optical Design (Gregory)
• Mechanical Design (Muller, Goble, Elias)
• Electronic Design (Rudeen)
79
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80
Outline: Optical Design
•
•
•
•
•
•
•
81
Overview
Foreoptics
Dispersers
Cameras
Performance
Materials selection and coatings
Background, stray light
Optical Layout

The layout shows a short camera in place in observing mode. Only the science
beam (not the wavefront sensor (WFS) beam) is shown. Light enters the
instrument from the lower left and encounters first a weak field lens, which is the
vacuum window of the dewar. The science beam is separated from the WFS
beam by a narrow pickoff mirror located at the position of the telescope focal
plane. The Offner relay optics reimage the focal plane onto the slit. More
important, it forms a pupil image where a cold stop is erected. Prior to the slit
there is a pair of filter wheels for defining the diffraction orders passed by the
instrument. From the slit the light goes to an off-axis paraboloid which collimates
the light. The collimated beam is dispersed in a direction along the slit by one
set of selectable dispersers (on the “prism” turret, which includes a simple mirror
for no cross-dispersion). The beam then passes to a set of selectable gratings
(on the grating turret) which disperses the light in the direction perpendicular to
the slit Finally the collimated beam is brought to a focus on the detector by one
of four cameras on a camera turret.
For field acquisition, a flat mirror is inserted just in front of the cameras,
intercepting the light from the collimator before it is dispersed. This permits
viewing the field without disturbing the dispersing elements for increased speed
and reproducibility.

82
Optical Layout
Grating turret
Collimator
f.l. 1494 mm
Camera
(short)
Pickoff mirror
Window
Slit
Offner Relay
Filter
Detector
Acquisition mirror position
Prism turret
83
Foreoptics




84
The purpose of the foreoptics is to reduce the level of background radiation in
the instrument.
The Offner Relay reimages the telescope focal plane onto the slit,
achromatically, 1:1 and with a very low level of aberration. The combination of
the entrance window of the dewar (which is a weak lens) and the primary of the
Offner (in first pass) makes an image of the aperture stop of the telescope (the
secondary) on the secondary of the Offner.
At the secondary, a black, circular, baffle is erected to suppress light from
outside the telescope beam. Additional baffles will be erected before and after
the secondary to further suppress out-of-beam light. On the second pass off the
primary, the beam is restored to telecentricity. This has the important result that
the next image of the pupil in the spectrograph falls one focal length from the
collimator mirror, where it is convenient to place the gratings and other
dispersers.
Cold filters before slit restrict optical bandwidth entering spectrograph, for ordersorting and suppression of out-of-band radiation.
Foreoptics
Entrance window
To OIWFS
Pickoff
Filter
Fold mirrors
Slit
Plane
secondary
Offner
Relay
Cold Stop
primary
85
Gratings and Prisms

Two turrets hold sets of gratings (3) and cross-dispersers (3, plus a
mirror) to provide several dispersing modes, allowing the user of the
instrument to make tradeoffs between:
 Spectral coverage vs resolution
 Slit length vs spectral coverage (cross-dispersion)

as well as to add a simple capability for polarimetry
Prism turret:





Prism – for short camera; spectral resolution 1800
Prism – for long camera; spectral resolution 1800
Wollaston prism (for polarimetry)
Mirror – for long-slit spectroscopy (100 arcsec with short camera; 50
arcsec with long)
Gratings:
 10.44 l/mm - (R= 590 short camera, 1770 long camera)
 31.7 l/mm - (R = 1800 short camera, 5500 long camera)
 110.5 l/mm - (R = 6000 short camera, 18000 long camera)
86
Gratings
Resolution
Grating Long Short
10.44 l/mm 1770
590
31.7
5500 1800
110.5
18000 6000
87
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88
Prisms
Order:
.87u
.94
Cross-dispersion options:
•Prism for short blue camera
•Prism for long blue camera
•Wollaston prism
•Mirror for long-slit work
1.10
7th
1.32
6th
1.65
5th
4th
2.20
2.37
3rd
1024 pixels
89
Long Blue camera; cross-dispersed
Cameras


90
Four cameras are provided:
 2 long for high spatial resolution (2 pixels matched to 0.1 arcsec
slit); optimized for 0.9-2.5 and 3-5 microns respectively.
 2 short for lower spatial resolution (2 pixels matched to 0.3
arcsec slit); longer slit and most importantly, higher throughput
under conditions of poorer seeing; again, optimized for shorter
and longer wavelengths respectively.
The long cameras (1305mm focal length) must be folded to make them
con-focal with the short cameras.
Cameras
Two short cameras, 0.9-2.4 microns,
3-5 microns. 0.15 arcsec / pixel
1 meter
Two long cameras, 0.9-2.4 microns,
3-5 microns. 0.05 arcsec / pixel
91
Design Performance
Post-slit optics
Percent degradation of rms image diameter, as measured on detector:
------worst case----Allocated to:
Allocated to:
surf.
tilt/wedge decenter
total
(rad.,irreg.) [degrees]
[mm]
Collimator
2.6% Fabrication
1.3%
2.0%
0
Assembly
1.4%
0.0%
0.008
0.1
Prism
1.0% Fabrication
1.0%
1.0%
0
Assembly
0.0%
0.0%
0
0
Grating
1.0% Fabrication
1.0%
1.0%
0
Assembly
0.0%
0.0%
0
0
Camera
3.6% Fabrication
2.7%
1.0%
Assembly
2.3%
0.0%
0.0058
0.02
Total (RSS)
Requirement
92
4.6%
5%
Evaluated at 1.2 microns. Worst case camera,
grating and cross-disperser is used.
Design Performance
 Wavelength coverage: 0.9 - 5 microns
 Field of view:
– 50 arcsec slit with long camera (6 arcsec crossdispersed)
– 100 arcsec with short (10 arcsec cross dispersed)
 Spectral resolution 600 -18,000
 Imaging: <5% degradation (>85% of light in 27
micron pixel)
 Throughput: at 2.2 microns, peak, with long
camera and 10.44 l/mm grating:
>54% with detector
93
>60% without detector
Materials




94
Transmissive cameras: use barium fluoride, calcium fluoride and SF6.
All well characterized in IR and at low temperatures (we contracted the
measurement of CTE and index of SF6 data at low temperatures).
Powered mirrors (Offner and Collimator) are diamond-turned Alumiplate
on aluminum for athermal optical performance and very low scattered
light.
Flat mirrors are on glass substrates which are economical and have
unsurpassed surface regularity and smoothness. (Typical reflectivity
99%)
Coatings: The diamond turned reflectors are all coated with protected
Au (for robustness). The glass mirrors are bare gold coated. The
transmissive optics are all coated with multi-layer anti-reflection
coatings. (Typical average transmission: 98% per element)
Materials




95
Transmissive cameras
Diamond turned Offner and Collimator
Flat mirrors: Glass
Coatings
Stray Light
We aggressively reduce extraneous sources of light. This topic may be
revisited in the discussion of the thermal design, but it is convenient to
summarize the various approaches being used:
 Low operating temperature (<65K)
 Scattered light:
 No obstructions in beam to scatter
 Low-scattering surfaces
 Baffling will be based on scattering analysis
96
 Cold motors to eliminate feedthroughs from ambient temperatures
(and active removal of heat evolved by motors)
 Thermal stationing of electrical feedthroughs
 No light leaks:The entire low-temperature portion of the
spectrograph from the pickoff mirror to the detector will be enclosed
in a nearly isothermal enclosure at <65K. Joints will be baffled by a
labyrinth construction. Path for vacuum pumping interior of
instrument will be provided for. The cold, light-tight enclosure will be
thoroughly light-leak tested at room temperature.
Stray Light
 Low operating temperature (<65K)
 Scattered light:
 No obstructions in beam to scatter
 Low-scattering surfaces
 Baffling will be based on scattering analysis
 Cold motors to eliminate feedthroughs from ambient
temperatures (and active removal of heat evolved by
motors)
 Thermal stationing of electrical feedthroughs
 No light leaks!
97
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98
Mechanical Design
•
•
•
•
99
Structural Design (Goble)
Mechanism Design (Muller)
Handling (Elias)
Thermal Design (Elias)
Internal Mechanical Configuration
OIWFS Detector group
Focal plane # 3
OIWFS Filter
wheel
Lens group
Gimbal
mirror
Collimator
Grating turret
OIWFS
field lens
Slit slide
IFU’s, Focal
plane # 2
Pick off, Focal
plane # 1
Long cam fold flats
Entrance
Window
Camera turret
Prism turret
Offner relay
Decker slide
Filter wheels
100
Detector, Focal
plane # 4
Flip mirror
not shown
Previous view looking from the bottom
101
Start
Requirements
Gravity flexure
Thermal conduction
Thermal expansion
Stress
Dynamic loading
Temperature
Consider heat flow
Steady state
Thermal Model
102
Structural Design Procedure
Strategy
Material selection
Select fabrication process
Maintenance access
Define structural geometry
Mechanical desktop solid
NASTRAN Model
Structural
Thermal stress
Simple design rules
Complete
Design
Requirements
for Structural
design
Gravity flexure
Alignment to telescope
+/- 620 micro rad
Applies to instrument rigid
body motion
+/- 1 micro rad for summed
effects of thermal and
flexure on optical bench
Stress
Low in bench <300psi
for gravity loading
1.5 yield margin on
handling of 20 g
103
Thermal conduction
Steady state temperature
gradients < 1 degree C
Dynamic loading
Transportation
Handling
Cryo head vibration
Thermal expansion
Match expansion of the
materials in assemblies
Temperature
60 Kelvin bench
30 Kelvin detector
Structural Design Strategy
• More flexure of Instrument support is allowed because of the
OIWFS, tilt < +/- 0.62 mrad. Optical bench must be very stiff,
displacement of the image on the detector < 2.7 micron for 15
degree change in gravity vector, ~+/- 1 microrad
• Central Dewar bulkhead supported on trusses, incorporates
mechanical, electrical, and thermal interfaces; Dewar end caps
have minimal complexity to reduce weight, fabrication cost, and
allow access to the bench parts
• The optical bench is a three dimensional Aluminum casting.
Structure is divided at the optimum places, Offner, forward
bench, center bench, aft bench. The internal bulkhead truss
connects to the center casting.
• Boxes that contain the mechanisms are the structure thus
saving weight and enhancing heat transfer.
104
Structural Design Strategy
•
•
•
•
•
105
Mounting flexure vs Bench flexure
Use of trusses
Central bulkhead for all interfaces
Three dimensional Bench
The Box is the Structure
Bench Support
 A set of 6 G-10 spokes between the Dewar bulkhead and the
center bench casting supports two lateral degrees of freedom
and twist about optical axis.
 Rigidity, ~ 60 Hz lateral resonance, more FEA later
 Thermal expansion compensating geometry
 Low thermal conduction, space between used for wiring,
cryo system, and radiation shield support
 Set of 3 G-10 support flexures constrain the focus translation,
and tilt about X and Y.
 Design provides mount of bench while cold and also can be
used to hold bench for maintenance while the cover is removed
from Dewar
106
Optical Bench Support
Bulkhead casting
Cryo-cooler
pair
107 Front cover side
G-10 fiberglass spokes
support laterally and
twist
G-10 flexures
support tilts
and focus
Center bench
casting
Rear cover side
Main Bench Assembly
 Center section supported on Dewar bulkhead with truss; truss
design to compensate for material contraction on cool-down
 Bench is totally closed to light except for entrance window. There is
a pumping port, opened by the acquisition mirror drive, to be used
during cool-down. Bulkhead will have a permanently mounted
Turbo pump to be used during temperature transitions
 Enclosed volume is connected boxes (mostly of Aluminum
castings) designed to fit around the mechanisms
 Most mechanisms are inside with access covers
 Outside parts are:
 Drive motors, shafts have light baffles, cold stationed to first
cooled radiation barrier (except for 2 OIWFS motors)
 OIWFS gimbal mirror
 Camera/focus/detector assembly
108
Optical Bench, front view
OIWFS bench
Long camera folds,
cover not shown
Gimbal mirror drive
is outside
Collimator
cover
Front bench
Dewar window
location
Aft bench casting
not shown
Camera access,
cover not shown
Bench center section
Pickoff
Offne
r
Support truss,
lateral flexures
not shown
All drive motors are cold
109
Detector and
Focus are outside
OIWFS Assembly
 Main OIWFS components mount on sub-plate
 Includes all components except field lens (that is, combination lens
group, gimbal mirror, filter wheel, Shack-Hartmann/detector
assembly)
 Allows external alignment of critical components
 OIWFS can be removed and tested or worked on without loss of
alignment; this can be in parallel with other GNIRS work
110
OIWFS Bench
Gimbal mirror
assembly mounted
on outside
Cover and element
mounting base
Center section
casting
Collimator/Camera
lens group
Filters, drive motor
inside
Detector assy,
only the lenses
shown
Focus stage,
drive motor
inside
Bench box casting attaches to
the center section with screws
111
Field lens
mounted in
forward bench,
bench not shown
Pre-Slit Optics
 Pick-off mirror spans the field of view with 3 point mount at
edges. Two points on one end, one on the other.
 Offner entrance fold mirror is 3 point mounted. The points are on
the front side of the mirror.
 Offner primary and secondary mirrors are Diamond turned 6061
Aluminum with Alumiplate surface. Structural housing is also
6061 Aluminum.
 Exit fold mirror is also mounted to three points on the front
surface.
 Assembly can be tested as a unit.
112
113
Spectrograph Bench








114
The slits and IFUs are supported in the forward bench casting which is not
shown in the picture.
Aft bench is the only structural part of the system not enclosing optics. Its
function is to support the collimator mirror in a cantilevered manner.
Collimator mount has a cover over the mounting details. The 3 blade flexure
mounting is shimmed for adjustment.
Prisms are mounted on a turret with a horizontal bearing axis. The spindle is
shown but the mount lugs are not.
The Gratings are mounted on a turret with a vertical axis. One drive does the
swap and the variable tilt. The axis being orthogonal to the prism axis allows the
non-detented drives to compensate orthogonal alignment.
The acquisition mirror is being designed to rotate up into position from below.
Not shown in the picture. The drive will incorporate over travel to open a 100
mm diameter pump hole.
The long cameras use the same two stationary fold flats.
Detector mounting and focus is being designed. The focus drive range will be 16
mm to allow testing warm with a different chip. The alignment on the stage will
be done using a shim. Cold strapping and thermal control of the detector is the
same as our other Aladdin mounts.
Spectrograph Bench
Bench aft section
not shown
Gratings, 3
on turret
Acquisition mirror
not shown
Collimator mirror
mount, cover not
shown
Bench center
section
Long camera fold
flats are stationary
4 Cameras, red &
blue, short & long
on turret
Slit Focus
Prisms, 3 plus a
flat mirror on turret
115
Aladdin detector,
on a focus stage and
light sealed with bellows
Front Cover Access







116
All of the pre-slit optics, the prism turret, the OIWFS field lens, and cold heads
are accessible from the front cover end of the instrument. Any extended service
time such as removal of the forward bench also requires back cover removal first
to remove the Aladdin Chip for safe vacuum storage. Servicing the cold heads is
possible by removing only the front cover as long as the instrument was back
filled with dry N2, the valve is closed, and a temporary cover is used on the optics
input hole.
The Offner can be directly removed if needed.
Filter wheels are changed by removing the assembly from the side of the forward
bench and then swapping filters. Filters are pre-mounted in filter cells.
Decker slide, slits, and IFUs are serviced by first removing the assembly from the
other side of the forward bench and disassembly as required.
Motors are mounted outside so therefore are accessible, however the gears and
bearings are inside on each assembly.
Prism turret work will require first removing the forward optics bench from the
bench center section.
Cryo-head replacement requires disconnection inside before extraction from the
Dewar bulkhead.
Front Cover Access
Cryo-coolers
Prism turret
Filter wheels
Offner & Pick-off
Slit & Decker
slide
Front bench
117
Rear Cover Access

All other parts, LN2 pre-cool assembly, wiring, gratings,OIWFS, cameras,
collimator mirror, acquisition mirror drive and valve, and detector/focus are
accessed from the rear cover.
 Collimator mirror mount is made so that the mirror could be removed for coating
without need for realignment.
 Camera turret can be removed from the bench as a unit or each camera can be
taken out individually.
 Detector can be removed while leaving the focus stage attached.
 Grating turret is on a sub-plate that is the cover. The center of the turret has a
guide pin so that the gratings cannot bump the center section during insertion.
 OIWFS parts are mounted onto the OIWFS bench cover plate. First the plate is
removed and then the bench can be detached from the center section. The
gimbal mirror can be removed without disturbing the bench.
 Acquisition mirror, cooling vacuum valve and pumpout port, are a unit mounted
on another plate that forms the cover on the bottom of the center section when
installed.
 The rapid cool LN2 pre-cool assembly is clamped to the top of the center section
with fill, vents, and valves passing through the bulkhead directly above (not
118 shown).
LN2 cooler
not shown
OIWFS sub-plate forms
cover of OIWFS bench
which is removable
Long camera
fold mirrors
Wiring and connectors
through bulkhead
not shown
Aft bench casting
not shown
OIWFS Gimbal
mirror on outside
Detector, removal is always
needed
119to protect it during
open periods
Cameras, access cover
not shown
Grating turret
through bottom
Collimator mirror,
cover not shown
This page intentionally left blank
120
Mechanism Design Flow Chart
Start
Requirements
Repeatability
Life
Speed
Temperature & Vacuum
Pick Design Concept
Warm or cold motors
Detents or not
Encoders or not
Stepper or DC motors
Control friction?
Home switches?
Limit switch strategy?
Backlash compensation?
Design
Solid model
Kinematic Analysis
Mathcad calculation
Select Mat’l & Parts
Thermal Expansion
Wear rates
Lubrication
Prototype Test
Calc Gear Ratios
Qualified Design
121
Mechanism Design Concepts









122
Use cold stepper motors. No feed through shafts. Concerns about light leaks
around shafts eliminated. Control of heat and radiation from motors requires
attention.
Cold motors simplify mechanical design.
Open loop control. Count steps from home position to desired position.
Simplifies control algorithms. Reliable and proven.
Open loop control simplifies design. No ratchets, detents.
Always drive mechanism to final position from one direction to remove backlash.
Positioning from opposite direction requires over-travel and reverse maneuver.
Mechanical datum switches define home positions. Datum switch assemblies
contain 2 switches for reliability.
Turrets are balanced to prevent motion induced by gravitational vector changes.
Friction brakes hold turrets in position against backlash and dynamic forces.
Use small, low-torque motors with large gear reductions to meet positioning
requirements and provide required drive torque for large mechanisms. Current
limiting can provide mechanism protection plus reserve torque if needed.
Mechanism Design Concepts
•
•
•
•
•
•
123
Linear & Rotary Mechanisms
Cold Motors
Open Loop Control
Redundant Datum/Limit Switches
Friction Brakes
Small Motors + Gear Reduction
GEAR DRIVE RATIOS FROM SDN0002.13
Mechanism
Range
of
travel
Filter Wheel 1 Infinite
&
Filter Wheel 2
Decker Slide
10 in
Table 1 - Drive Gear Ratios
Repeatabil Type of
Gear ratio
ity
Drive
Ring &
Pinion
312/15, 24
pitch
0.76
mrad
4160/tur
n
50 micron
Rack &
Pinion +
Gear
reduction
Screw +
Worm
Gear
reduction
Rack &
Pinion +
Gear
reduction
Worm +
Gear
reduction
Worm +
Gear
reduction
Worm +
Gear
reduction
Screw + Gear
reduction
.4375 Pitch
dia + 2/1
gear
43.6
micron
2910
0.2 inch
pitch + 30/1
worm
0.423
micron
352,500
.4375 Pitch
dia + 2/1
gear
43.6
micron
1746
180/1 worm
+ 2.5/1 gear
.035
mrad
75,000
180/1 worm
+ 2.5/1 gear
.035
mrad
75,000
180/1 worm
+ 2.5/1 gear
.035
mrad
85,000
0.2 inch
pitch + 3/1
gear
4.23
micron
2250
11.75 in 1 micron
Acquisition
Mirror Slide
6 in
Prism Turret
300 deg .037 mrad
50 micron
Grating Turret 300 deg .037 mrad
Camera Turret 340 deg .07 mrad
124
0.75 in
Range
(steps)
3.7 mrad
Slit Slide
Detector
Focus Stage
½ motor
step
6 micron
Mechanisms
• Linear
–
–
–
–
Decker Slide
Slit Slide
Detector Focus
Environmental Cover (external to instrument)
• Rotary
–
–
–
–
–
125
Filter Wheel (2)
Prism Turret
Grating Turret
Camera Turret
Acquisition Mirror
Slit/Decker Module
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Example of a linear mechanism (similar concept used for decker slide and focus
drive)
Module view shows location of slit slide (and decker slide)
Key points:
 Slit slide runs on rollers, spring loaded.
 Motor is thermally de-coupled from mechanism to minimize heat and
radiation effects
Prototype of a linear mechanism will be built and tested to minimize risk
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Gear Drive
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Inverted ACME Screw/Nut Design
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Long Nut (Stretch nut and cut in half)
Short Screw
Athermal design
Drive Details
 Initial reduction with worm/wheel (Vespel/brass)
 Final reduction with linear nut, split screw (Vespel/Al)
 Split screw reduces backlash, final positioning in standard direction can limit
it further
 Use Vespel for minimum wear
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Slit Slide Assembly
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Slit Slide Assembly
 Shows location of pockets for 2 IFU modules, including datum locations for
assembly
 Shows slit module and its location
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Removable Slit Module
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134
Slit Module Assembly
 Holds slit plate, pupil viewer lens (other lenses in filter wheels)
 Slit plate manufactured as a unit, provides precise control of slit-to-slit
alignment
 Slit plate can be replaced in future if needs evolve
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Grating Turret
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Rotary mechanism. Similar design used for prism, camera turrets, filter wheels and
acquisition mirror.
Rotating part moves <360 degrees, holds 3 gratings
 Large central post, two bearings define position
 Friction brake plus final motion in standard direction eliminate backlash
Same axis of motion is used for both grating selection, tilt (requires slightly longer
gratings, small motions of footprint on cameras, both effects limited by design).
Motor thermally de-coupled from mechanism support, can be shielded to eliminate
thermal, radiation effects.
Entire mechanism mounts on sub-plate that bolts to bench
 Permits external alignment and test
 Removal and installation without loss of overall alignment (installation to machining
tolerances is sufficient)
Adjustments provided for individual grating alignment (needed to co-align rulings).
Drive is initial gear reduction plus final worm/wheel reduction.
Prototype of a rotary mechanism will be built and tested to minimize risk shown.
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Home Switch and Parking Brake
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All mechanisms requiring precision positioning use a repeatable, redundant, parallel
spring flexure home switch.
Use on filter wheels, decker and slit slides,prism, grating, turrets, and detector focus.
Home switch will be tested to characterize repeatability.


Friction brake used on rotary mechanisms.
Final drive worm wheel will also serve as a brake disk.
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139
Configuration Management Tools
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140
Established Database based on experience gained on 2 previous successful
instrumentation projects.
Use database to define drawing/assemblies, track progress of part from design/
draft through fabrication and final assembly.
Engineer defines Drawing Breakdown Structure (DBS) and assigns tasks to
designers/drafters.
Compare budgeted weight with calculated/measured weight and adjust budget
accordingly.
Tool to flag over budget conditions early so that corrective action can be taken.
Make status reports for on a periodic basis for status meetings.
All mechanical designs are being solid modeled. Reduces errors and increases
confidence.
Extract mass properties from solid models. Weight, CG, Moments of Inertia.
Solid model files named per DBS.
Configuration Management Tools
• Microsoft Access Database
–
–
–
–
Drawing Breakdown Structure (DBS)
Weight Budget
Project Tracking
Customize Database as needs evolve
• Autodesk Mechanical Desktop
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–
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Solid Modeling
Mass Properties
Interference checking
Produce 2D fabrication drawings
142
Handling complies with
Gemini interfaces
• Instrument can be installed in up-looking or
horizontal position
• Provides proper interfaces to Gemini handling
equipment (cart, hoists)
• Interface to ISS similar to Gemini ballast
weight assemblies (better locating features
needed)
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Thermal Design
• Meets Gemini cool-down requirements
• Provides optical stability for OIWFS and for
camera and collimator focus
• Meets Gemini warm-up requirements
145
Instrument Cool-Down
 Liquid nitrogen pre-cool system
 Accelerates cool-down to ~80K
 Can be by-passed
 Recommended by review committees
 4 cryocoolers
 Required for cool-down from 80 to 60K
 Supplement pre-cool; can be used alone
 Cool-down meets 4-day Gemini requirement
 Cool down with cryocoolers alone close to 4 days
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Instrument Cool-Down
• Liquid Nitrogen Pre-Cool
• 4 Cryocoolers
• Meets 4-day Gemini Requirement
147
Thermal Stability and Control
 Radiation shield design minimizes thermal gradients in optical
bench
 Main effect of gradients in current design is on collimator and OIWFS focus
 Baseline design is 2 “floating” shields, 1 active shield
 Use of MLI possible (either as thermal or weight risk mitigation)
 Active thermal control of bench required
 Without control, will see temperature variations due to variations in ambient
temperature, motor use (and control protocols) and in cryocooler
performance
 Temperature control is needed to ensure stable performance of OIWFS
(ability to maintain guide star on slit) -- recommended by ICD
 Temperature control also simplifies software control of camera focus (would
otherwise need a correction for bench temperature)
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Thermal Stability and Control
• Radiation Shield Design Minimizes Gradients
• Active Thermal Control of Bench Required
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Instrument Warm-Up
• Distributed Heaters Provide Rapid Warm-Up
• Stand-Alone Control Box Provides Off-Line
Warm-Up
• Warm-Up Meets 1-Day Gemini Requirement
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Dwg #89-NOAO-4201-5025 (postscript),
shown here in book
Title: Instrument External Cabling diagram
B-sized copy in review books (hardcopy)
A-sized viewgraph for R. Rvw is used
(for reference only)
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GNIRS ELECTRICAL
DESIGN
 System Overview
 Control Architecture
 Electrical Packaging
 Spectrograph Controller packaging
 Thermal Enclosure
 ALADDIN Detector Controller packaging
 Thermal Enclosure
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GNIRS ELECTRONIC CONTROL ARCHITECTURE
Gemini LAN's
A&G SDSU
VME I/F
(data/control fiber)
(control LAN)
(data &
control)
(control LAN)
OIWFS Mech Ctlr
Detector Thermal
Control
OIWFS Detector
Controller (SDSU)
Spectrograph Ctlr
Mechanisms (motors,
limit and home
switches)
Mechanisms
Cryocooler Control
(on dewar)
CISCO PORT
SWITCH HUB
ALADDIN Array Controller
Detector Controller
Data Processing
Dewar Health
Temperatures
Detector Thermal
Control
Vacuum
Manual Setpoint
Manual Control
Dewar Warm Up
THERMAL ENCLOSURE #1
156
Dewar Thermal Control
THERMAL ENCLOSURE #2
Instrument Sequencer Controls
Three Subsystems
• Spectrograph Controller,
Thermal Enclosure #1
• OIWFS Controller, Gemini-furnished,
Thermal Enclosure #1
• ALADDIN Array Controller, Geminifurnished, Thermal Enclosure #2
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Dwg #89-NOAO-4201-5020 (postscript),
Title: Spectrograph Control schematic Block Diagram
shown here:
B-sized copy in review books (hardcopy)
A-sized viewgraph for R. Rvw is used (this viewgraph
is for reference only - isn’t shown initially)
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Spectrograph Controller
Architecture is Complete
 Addresses all Gemini interface requirements
 All major functions identified
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Mechanism control
Cryocooler control
Dewar thermal control
Dewar health (vacuum/temp sensing)
 All individual cards identified
 All control interfaces defined
 Dewar wiring, cable/connector pinouts remain
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Dwg #89-NOAO-4201-5011 (postscript),
Spectrograph TE Layout, Power,
Grounding schematic
shown here:
A-sized copy in review books (hardcopy)
A-sized viewgraph for R. Rvw is used
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Electronics is Contained
in Two Cabinets
 Spectrograph Thermal Enclosure
 Array Controller Thermal Enclosure
 Additional External Electronics mount on
dewar
 Set by detector requirements
 ALADDIN preamp
 OIWFS SDSU2 controller
 Stand-alone warm-up controller box
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Sub-System Integration
 3 Externally Provided Sub-Systems:
 IFU
 OIWFS
 Array Controller
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IFU
 Provided by University of Durham through
IGPO
 Two modular sub-assemblies
 Aligned and tested prior to installation
 Space provided on slit slide
 Installed and aligned to datums, following ICD
 Final alignment check during GNIRS
integration
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OIWFS
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Provided by IfA, Hawaii through IGPO. Includes optical components and subassemblies, packaged controller, electronics boards and subassemblies, test
cables, software, alignment and test procedures
Optical components and mechanisms mount on modular bench assembly
Optical component integration ties to ICD, includes alignment procedures and
tolerances
Electronics require wiring and cabling within GNIRS
Electronics require installation of controller hardware, which includes Leach
(SDSU2) controller mounted on dewar bulkhead structure and components
controller mounted inside instrument thermal enclosure
Testing capability limited to low-level tests (supplied by IfA); essentially limited to
functional testing of devices and detector. This is sufficient, in principle, to check
instrument flexure (OIWFS to slit).
OIWFS
• Provided by IfA, Hawaii through IGPO
• Opto-mechanical assemblies mount on bench
structure
• Requires integration and alignment of
assemblies
• Requires installation of controller hardware,
wiring and cabling
• Limited testing of capability
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Array Controller
 Provided by NOAO through IGPO
 Requires integration of hardware
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Detector
Pre-amplifier
Thermal enclosure
Wiring and cabling
System Integration & Test (1)
 Critical Assumptions:
 Sub-systems can be tested externally and independently. These
tests include tests of mechanism flexure, cold tests of functionality
(repeatability, torque requirements). Alignment of components
within mechanism or modules, where required, can also be done
externally (e.g, gratings within turret).
 Minimize alignment procedures. This implies design of appropriate
interfaces (and proper location) so that assembly tolerances are
controlled and are sufficient to meet alignment requirements.
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System Integration & Test (1)
 Critical Assumptions
 External Tests and Alignment of Sub-Systems
 Minimize Alignment
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System Integration & Test (2)
 Integration and Alignment Plan
 Sub-systems are assumed to have been “pre-tested” and to have
their optics aligned (if required); system test is therefore primarily a
test of the instrument as a whole and not of functionality of
individual mechanisms.
 Testing vacuum and thermal systems is carried out in two stages
and precedes testing of the complete instrument in order to isolate
any problems in these areas as early as possible.
 Assembly and warm test of the bench with mechanisms provides
access for diagnosis. It includes testing for light leaks.
 Final integration and cold testing covers full instrument functionality
(partial for OIWFS).
176
System Integration & Test (2)
 Integration and Alignment Plan
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Sub-systems “pre-tested”
Test vacuum and thermal systems
Assemble and warm test bench
Integrate and cold test
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System Integration & Test (3)
 System Tests Include:
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Functionality
Repeatability
Flexure
Thermal (cool-down, warm-up, stability, gradients)
Optical (image quality, background [light leaks and
scattering], throughput)
 Configuration characterization
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SECTION VII
Risk Identification and Mitigation Plan
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Risk Items
 Risk Items pointed out by the Committee
 Thermal (Instrument cool-down and thermal
gradients)
 Optical (Focus control, alignment procedures, mirror
finish, light leaks)
 Handling
 OIWFS Integration and Alignment
 IFU Integration
 Additional Risk Items
183
 Software
 OIWFS performance
 Mechanism repeatability
Risk Mitigation Table
Impact = Consequence of Failure on Science Productivity of Instrument
Risk = Probability of Failure Despite Mitigation Plan
Item
1
Areas of Concern
Thermal
-Long Cooldown Time
Current
Impact Risk Level
LOW
Central Positioning of Cryocoolers
LN2 Precool
Active Thermal Bench Control
Reduced Cold Mass
LOW
Central Positioning of Cryocoolers
Active Radiation Shield
Minimize Bolted Joints
Ability to Cold Strap Cryomotors
Active Thermal Bench Control
HIGH
LOW
Detector Focus Mechanism
Active Thermal Bench Control
MEDIUM
LOW
Cleaner Optical Design (fewer folds)
Modular Mechanisms
Sub-system Alignment outside GNIRS
Simplified Alignment Procedure
Detector Focus Mechanism
-Diamond Turned Mirrors MEDIUM
LOW
Now only 3 Diamond Turned Mirrors
Glass Substrate Flat Mirrors
LOW
-Temperature Gradients MEDIUM
and Stability
2
Optical
-Detector Focus
-Optical Alignment
184
Mitigation Plan
Risk Mitigation Table (cont)
Item
Areas of Concern
-Radiation Shield Gaps
Current
Impact Risk Level
HIGH
LOW
Mitigation Plan
Internal Motors (no feedthroughs)
Spectrograph Completely Enclosed by Bench Structure
Instrument Conforms to Gemini Interfaces
Bulkhead Design Leads to Easier Assembly/Alignment
3
Handling
MEDIUM
LOW
4
OIWFS
-Assembly/Alignment
MEDIUM
LOW
Now Essentially Independent Module
Use IfA Layout (except 2 fold mirrors)
ICD Complete
MEDIUM
HIGH
Active Thermal Bench Control
Operational Alternatives with PWFS
LOW
LOW
ICD Nearing Completion
Repackaged as Self-Contained Units, Install in Slit Mechanism
MEDIUM
HIGH
Only IFU Operation Affected
-Performance
5
IFU
-Assembly
-Performance
6
Mechanisms
MEDIUM MEDIUM Prototype Linear/Rotary Mechanisms
Cold Test of Critical Functions on Prototype
(cooldown, torque, repeatability, absolute positioning, flexure)
Cold Test Completed Mechanism
7
185
Software
MEDIUM MEDIUM Engineering Test Software Developed for Integration/Testing
Instrument Can be Tested Without Gemini Software
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Risk Mitigation Plan
 Risk Mitigation Table
 Prototyping of mechanism drives
 Mechanism testing
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SECTION VIII
Conclusion
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Summary
• We have presented the current status of the
project and engineering design
• NOAO has put into place the required engineering
team and management structure
• GNIRS is a new design configuration which
addresses committee concerns and risks
• We have the required resources in place
• The GNIRS instrument will deliver in mid-2002
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