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HIRDLS
SPARC Applications and Development Status
John Gille
University of Colorado and NCAR
John Barnett
Oxford University
Alyn Lambert, David Edwards, Christopher Palmer
Michael Dials, Chris Halvorson, Eric Johnson, Wayne Rudolf
Ken Stone, Bob Wells, John Whitney, Douglas Woodard
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HIRDLS Scientific Goals
The primary goals of the High Resolution Dynamics Limb Sounder
(HIRDLS) experiment are to acquire data with which to investigate
1) the recovery of the ozone layer following the phase-out of some
halogen-containing chemicals;
2) the role of the upper troposphere and lower stratosphere (UT/LS) in
climate; and
3) the chemistry of the upper troposphere.
2
Recovery of the Ozone Layer
•
•
•
•
•
Stratospheric chlorine is predicted to decrease as a result of the
Montreal Protocol and subsequent agreements
Chlorine abundances are decreasing in the troposphere, and now, in
the stratosphere
The recovery of the ozone layer with decreasing Cl will be complicated
by the lower temperatures in the lower stratosphere, due to greenhouse
effects as well as the reduction in ozone itself
HIRDLS, and the Aura spacecraft, will fly during the unique period near
the maximum loading of stratospheric chlorine. It will be important to
acquire a record of atmospheric composition and behavior during this
singular period.
One of the goals of HIRDLS is to document this period in the
atmosphere, and use these data to understand ozone chemistry and
radiative effects in this unique period.
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Stratospheric Chlorine
A3
CH 3Br(A)
HCFCs
E E S C ( ppb )
3.0
Halons
CH 3CCl3
CCl4
2.0
CFCs
1.0
CH 3Br(N)
CH 3Cl
1960
1980
2000
2020
2040
2060
Growth of stratospheric chlorine according to various scenarios
Figure 1
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The Role of the UT/LS in Climate
•
•
•
•
The structure and behavior of the atmosphere around the tropopause
are now known to be more complex than previously thought.
Exchange of material between the troposphere and the stratosphere
takes place not only through ascent through the tropical tropopause,
but also through transports along isentropic surfaces that cross the
tropopause. These transports include those of radiatively active (e.g.
CO2, H2O, CH4, etc.) and chemically active (N2O, CFC11, CFC12,
H2O, etc.) gases that directly or indirectly influence the earth’s radiative
balance.
Many of these transports are on finer scales than have been observed
before. In addition, there are other features which lead to the formation
of fine scale filaments.
One of HIRDLS’ goals is to observe these small-scale transports and
subsequent mixing, and to clarify their effects in the climate system.
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Transport Features Observed by HIRDLS
Figure 2
(from J. Holton/UGAMP)
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Stratosphere-troposphere exchange on small scales
Passive tracers on the 320 K isentrope.
Coloured air is stratospheric, blank is tropospheric
Figure 3
[From Appenzeller et al. [1995]]
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UT/LS Chemistry
• HIRDLS measurements will extend down into the lower stratosphere
and upper troposphere when clouds are not too optically thick.
• Trace species in this region are rapidly transported over long
distances.
• HIRDLS will obtain measurements of:
O3, H2O, and HNO3, CFC11, CFC12, CH4, N20 and aerosols.
• These data will greatly augment knowledge of composition and
transports at these levels.
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Summary of Measurement Requirements
Temperature
<50 km
>50 km
 0.41 KK precision
absolute


1 K precision
2 K absolute
Constituents
O3, H2O, CH4, H2O, HNO3, NO2, N2O5,
1-5% precision
ClONO2, CF2Cl2, CFCl3, Aerosol
5-10% absolute
Geopotential height gradient
20 metres/500 km (vertical/horizontal)
(Equivalent 60oN geostrophic wind)
(3 m s-1)
Coverage:
Horizontal - global 90oS to 90oN (must include polar night)
Vertical
- upper troposphere to mesopause (8-80 km)
Temporal - long-term, continuous (5 years unbroken)
Resolution:
Horizontal - profile spacing of 5o latitude x 5o longitude (approx 500 km)
Vertical
- 1-1.25 km
Temporal - complete field in 12 hours
The LIMB Scanning Technique
Infrared radiance emitted by the earth’s atmosphere,
seen at the limb, is measured as a function of relative
altitude
Spectral Locations of the HIRDLS Channels
Figure 5
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Examples of Calculated Radiance Profiles
Channel 3 (CO 2, optically thick)
70
60
50
40
30
radiometric noise
apparent tangent height, h / km
80
20
10
0
10-4 10-3
10-2
10-1
100
101
atmospheric radiance, L / W·m–2·sr–1
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Driving Requirements on Accuracy and Precision
Retrieval based on N (h).
This leads to the most stringent requirements:
Radiance
Accuracy
1%
(temperature channels 0.5%),
Random noise1-12 x 10-4 Wm-2 sr-1 (channel dependent)
Sample spacing Accuracy
0.25%,
random error of 1 arcsec (1 ).
Requirements are divided between
- encoder on the scan mirror (motion relative to optical bench), and
- gyroscope on the optical bench (motion of bench in inertial space).
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HIRDLS Alternative Global Mode Sub-Tangent Point
HIRDLS Boresight Tangent Point Latitudes and Longitudes in the Alternative Global Mode
Figure 6
HIRDLS Instrument Consists of 9
Subsystems
IN-FLIGHT CALIBRATION SUBSYSTEM (IFC)
OPTICAL ITEMS AND ELECTRONICS TO
ENABLE RADIOMETRIC CALIBRATION
DURING FLIGHT OPERATIONS.
SUN-SHIELD SUBSYSTEM (SSH)
TELESCOPE SUBSYSTEM (TSS)
INSTRUMENT TELESCOPE AND
RELATED ELECTRONICS UNITS
POWER SUBSYSTEM (PSS)
PROVIDES BASIC POWER
CONVERSION AND
SWITCHING
•UK
•US
DETECTOR SUBSYSTEM (DSS)
MULTI-CHANNEL INFRARED
RADIOMETRIC DETECTOR ARRAY
AND DEWAR ASSEMBLY
INSTRUMENT PROCESSING
SUBSYSTEM (IPS)
SIGNAL AND DATA PROCESSING
TO SUPPORT MISSION SCIENCE
OPERATIONS AND
HOUSEKEEPING FUNCTIONS
GYRO SUBSYSTEM (GSS)
PROVIDES PRECISION BASE
MOTION DISTURBANCE DATA
STRUCTURAL THERMAL SUBSYSTEM (STH)
PRIMARY STRUCTURAL SUPPORT AND
ENVIRONMENTAL ENCLOSURE FOR
ELECTRONIC UNITS AND TELESCOPE
COOLER SUBSYSTEM (CSS)
PROVIDES ACTIVE CRYO-COOLING FOR
THE INSTRUMENT DETECTOR ARRAY
Figure 7
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INSTRUMENT SUBSYSTEMS - EXPLODED VIEW
Fixed Sunshield
(STH)
Sunshield-Door
(SSH)
Black Body Assembly
(IFC)
Optical Bench Assy.
with Shroud
(TSS)
External Connector
Bulkhead
Encoder Electronics Assy.
(TSS)
LEGEND
STH
SSH
TSS
DSS
GSS
CSS
IFC
PSS
IPS
Power Converter Unit
(PSS)
Telescope
Electronics Unit
(TSS)
Cooler Control Unit
(CSS)
Space-View Aperture
Assembly
(SSH)
Signal Processing
Unit
(IPS)
Gyro Electronics Unit
(GSS)
Detector Dewar
(DSS)
Baseplate
(STH)
S-Link
(CSS)
Cooler Radiator Panel
with Compressors & Displacer
(CSS)
Flexible Vacuum Enclosure
(CSS)
Gyro Mechanical Unit
(GSS)
Vibration Isolators
(TSS)
Black Body
Electronics Unit
(IFC)
Inst. Processor Unit
(IPS)
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Optical Schematic
Space
View
Port
Space View
Aperture Stop
Space View
Relay Mirror
Field Stop #2
&
Warm Filter
Assembly
Intermediate
Lyot Stop
Lens
Assembly
Ge Lens
#1
Space View
Field Stop
Albedo
Shield
Secondary
Mirror
Telescope
Subsystem
Structural Thermal Subsystem
Fold
System
Aperture
Stop
Out-of-Field Baffle
Field
Stop #1
Ge Lens
#2
Chopper
Radiation
Trap
Chopper
Mechanical Unit
Primary
Mirror
Primary
Diffraction
Baffle
(PDB)
Scan
Mirror
Sunshield
Door
"Hot Dog"
Aperture
In-flight
Calibrator
Black Body
DSS
Cold Filter
Assembly
Sunshield
Door
Aperture
Calibrator
Mirror
Fixed
Sunshade
Figure 8
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Figure 9
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Figure 10
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Structure Thermal Subsystem Status
Dummy MLI on Flight Structure in MMS Clean Room
Figure 11
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HIRDLS Calibration Facility
Clean room and vacuum chamber
Seismic isolator
Chamber optical bench
Monochromator turret
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Verification of 1 KM Resolution
True Temperature Wave
Retrieved Temperature Wave
0.1
true pressure, p / hPa
1
10
100
1000
-2 -1.5 -1 -0.5
0
0.5
1
temperature wave, T / K
1.5
2
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HIRDLS CAPABILITIES
80
PRECISION
MIXING
RATIO TEMP
(%)
(K)
15
10
Altitude (km)
60
5
1.
3
.5
1
.25
40
20
TEMP
HO
2
O3
NO
2
CH4
NO
2 5
NO
2
Figure 12
CFCl
HNO 3
PSC
Locations
CF Cl 2 Aerosol Cloud
2
Tops
Effects
3
ClO NO 2
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Summary
•
•
•
HIRDLS is a powerful and flexible instrument for the global
measurement from the upper troposphere into the mesosphere of
Temperature, 10 trace species and aerosols
New features are:
– Fine spacing of measured profiles in the longitudinal direction
(<500km)
– High vertical resolution (<2 km vertical wavelength)
– Ability to sound the upper troposphere and low stratosphere
(UT/LS) regions
– Measurement of many species with a range of chemical lifetimes
– 5-6 year instrument life
Standard data will provide long-term detailed data and important
insights into:
– Evolution of the ozone layer
– Climate processes, especially in the tropopause region
– Upper troposphere chemistry
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Additional information on HIRDLS can be found at the HIRDLS website,
http://www.eos.ucar.edu/hirdls/home.html.
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