Download SunRISE Proposal

II. Science Objectives
A. Sunrise and Small-Scale Physical
Processes
Both observations and theory/modeling
point to small-scale processes — those
acting at size scales comparable to (or
smaller than) a photospheric scale height —
as the agents that control the structure,
dynamics, and energetics of the solar
atmosphere at larger scales. The small-scale
processes are the source of solar variability
and, ultimately, solar influences on the
Earth. To illustrate the need for the high
angular
resolution
and
quantitative
diagnostics afforded by Sunrise, we briefly
explore only a few examples of important
small-scale processes:
 The mechanism by which the magnetic
field is concentrated into intense “flux
tubes” in the photosphere,
 The “cancellation” of magnetic flux, and
 The generation of MHD disturbances in
the photosphere, via interaction of flux
tubes with convective motions, and their
subsequent
propagation
to
and
dissipation within the upper layers.
At present, these processes are not well
understood, largely because of the lack of
continuous, quantitative measurements of
the magnetic field and related atmospheric
structure on the relevant size for dynamics:
the density scale height in the photosphere.
Observations needed to address these and
other important issues will involve
quantitative measurements of the vector
magnetic field, Doppler velocities, and
thermal structure. Even the best quantitative
field observations to date have angular
resolution roughly one order of magnitude
worse than that needed to spatially resolve a
typical elemental flux tube.
Theoretical mechanisms have been proposed
for each of the three examples, but
conclusive evidence in support of any specific
mechanism has generally eluded observational
investigation. Convective intensification (Parker
1978) is a popular explanation for the
coalescence of photospheric fields into tiny
kiloGauss flux tubes. Figure 1 presents one
frame of a numerical simulation of convective
intensification. These simulations suggest kiloGauss flux bundles form with diameters of order
100 km, and with dynamically important
internal structure at least as small as ~30 km.
Figure 1: Convective intensification of magnetic field in
a numerical simulation (Grossmann-Doerth, Schüssler &
Steiner 1998).
Shown is a vertical cut through the
photosphere and the upper levels of the convection zone,
with contour lines outlining the magnetic field. The
nearly horizontal curve indicates continuum optical depth
unity at 500 nm. A magnetic element with kG field
strength has formed through the combined effects of
magnetic flux advection by horizontal flow, radiative
cooling, and suppression of convection by the growing
magnetic field.
Reconnection followed by either resubmergence
or expulsion could explain the apparent
cancellation of unrelated flux bundles when they
are brought together by larger scale flows (such
as the supergranular flow). With very high
resolution time series of quantitative vector
magnetic field measurements and simultaneous
imaging and spectroscopy of chromospheric
structure, one may be able to ascertain heights at
which reconnection takes place. The relative
fraction of flux that undergoes resubmergence
Page 1 of 15
as compared to that which is expelled
upwards as buoyant U-loops will then be
determined. Figure 2 shows a region of
apparent flux cancellation within an active
region,
where
full
Stokes
profile
measurements indicate apparent contact of
opposite polarity flux.
Figure
2: Advanced Stokes Polarimeter
observations of the vector magnetic field in a newly
emerging active region reveal a contact region of
opposite polarities between the two large, oppositepolarity pores. Opposite polarities of nearly vertical
magnetic fields occur within the resolution size of
about 1”, as seen in the expanded perspective view in
the top plane where arrows represent the direction of
the field vector.
The vector field analysis indicates that the
field is concave upwards (“U-loop”), but
within the contact region there are no
extensive areas of horizontal field like those
encountered in typical (“-loop”) emerging
geometry. Apparently an angular resolution
much better than the 1 arc second
resolution of these observations will be
necessary to explore the physics of the
contact region. In the case illustrated here,
one would either find smaller-scale, rapidly
evolving regions with -loop geometry
indicating local reconnection, or persistent
U-loop geometry with horizontal fields
indicating the buoyant rise of U-loops through
the photosphere.
Simulations also reveal that granular convection
may induce propagating disturbances in flux
tubes (Steiner et al. 1998). This interaction has
long been suspected of producing heating of the
upper solar atmosphere via the generation and
upward propagation of MHD waves, but the
extremely high angular resolution needed to
detect these very small events in the
photosphere has eluded direct detection.
B. Rationale for a Resolution of 30 -100 km
A considerable body of observational evidence
indicates the presence of magnetic-related fine
structure on scales smaller than the highest
resolution yet attained. A few recent examples
follow:
 Magnetic Speckle Imaging:
Figure 3
illustrates the presence of Zeeman effect
polarization near the diffraction limit of a
large
ground-based
solar
telescope
(0.2 arcsec).
Figure 3:
Speckle imaging in combination with
polarimetry provides direct evidence for magnetic flux
concentrations at or below the angular resolution limit of
this large solar telescope: 0.2 arcsec. (Figure courtesy of
C. Keller and B. Wilton.)

Phase Diversity Reconstruction: With
post-facto image reconstruction one may
correct for atmospheric seeing. Figure 4
reveals many bright features believed to
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indicate the presence of intense
photospheric flux tubes in the
intergranular lanes. Some are at the
diffraction limit of the telescope (0.16
arcsec, 120 km on the Sun). One
objective of Sunrise will be to determine
the extent to which the intensity in the
G-band actually traces the magnetic
field.
Figure 4:
Phase diversity imaging aided by
adaptive optics reveals tiny, bright structures that are
unresolved at the diffraction limit of the telescope
(0.16 arcsec). These features are associated with
concentrations of intense magnetic flux. (Figure
courtesy of C. Keller.)

Stokes Profile Asymmetry: Departures
from symmetry in Stokes Q, U and antisymmetry in Stokes V spectra signal the
presence of gradients of the line-of-sight
velocity
and
magnetic
field.
Asymmetries are most pronounced
where the average flux density is low
(Solanki 1993, Sanchez Almeida et al.
1996, Sigwarth et al. 1999), i.e. where
convective motions have a larger
influence on the magnetic field. Line-ofsight gradients imply dynamical
structure on the scale of a photon meanfree-path, which is comparable to a scale
height. Observations of extreme
asymmetries may be reproduced by
atmospheric models having microstructure on scales small compared to a
photon mean-free-path (MISMAs, Sanchez
Almeida et al. 1996, 2000). Sunrise is
expected to provide much tighter constraints
on the distribution of magnetic fields and
motions leading to observed asymmetries.

Sunspot Fine Structure: Numerous
observational studies indicate that much of
the fine structure of sunspots remains
unresolved, even with the best image
reconstruction techniques available today.
Fine structure appears to be the essence of
sunspot penumbrae, where light and dark
filaments are intimately connected with the
Evershed flow. In sunspot umbrae, the tiny,
bright, transient umbral dots are integral to
the energy transport. Sunspot fine structure
holds the key to convective transport of
energy in a large-scale, strong magnetic
field.
C. Interplay of Theory and High Resolution
Observations: Solar physics relies increasingly
on numerical models to illuminate the physics
of varied solar phenomena. For magnetic fields
in the solar atmosphere, these models
incorporate progressively more sophisticated
physical descriptions, yet they still rely on
significant assumptions in terms of dissipative
processes, boundary conditions, etc. Because of
the small-scale nature of the physical processes
at work, modeling and simulations of solar
magnetic structures, ranging from the weak
internetwork flux through sunspot umbrae, all
require guidance from observations at the
highest spatial resolution possible. Theory,
modeling, and numerical simulations also
strengthen the case for very small structures:
 Discontinuous Field Evolution: Driven by
convective flows, the footpoint motions of
photospheric flux will lead to the
development of discontinuities of the
magnetic field in the atmosphere above
(Parker 1994).
The width of such
discontinuities in the non-ideal MHD case
depends on the conductivity of the plasma. It
Page 3 of 15


should be extremely small in the
photosphere where diffusion controls the
resistivity (Parker 1979). Indeed, MHD
numerical simulations in 3D generate
discontinuities (Galsgaard & Nordlund
1996).
Non-Linear
Dynamo
Models:
Numerical
models
of
magnetoconvection generate structure in the
magnetic field that is much smaller than
the structure in the flows. The dynamo
action of convective flows may then by
itself create very small-scale structure in
the photospheric magnetic field.
Diffusive
Dissipation
in
the
Photosphere: If molecular diffusion
limits the dissipation of magnetic fields
in the photosphere, then one expects
structure of the field on the scale of 10
km (Schüssler, 1986).
It has often been argued that visible
photospheric structure will be limited by
photon diffusion to an optical mean-freepath, i.e. about one scale height. This would
be true if scattering (i.e. non-LTE effects)
entirely dominate the emission and
absorption, but collision rates are large in
the photosphere, so the emission in most
photospheric diagnostic spectral lines is
thermal. The result is that structure on scales
much smaller than the photon mean-freepath may be detected, even in an opticallythick situation (Bruls & von der Luhe, 2001)
Indeed, synthesis of line profiles from
dynamical flux tube simulations suggest that
visible structure in Stokes V will exist down
to size scales of 5 km. In chromospheric
lines, non-LTE effects (scattering) often
dominate the excitation. Even in this case it
is possible to detect structures much smaller
than a photon mean-free-path. Under the
condition that the structures are opticallythin, tiny, hot, dense structures (i.e., the site
of reconnection) would still appear highly
localized, albeit with a scattering “bloom”
surrounding the dense structure.
These
considerations, along with the observational and
theoretical indications above, strengthen the
case for solar observations of the highest
angular resolution possible.
D. UV Diagnostics
At balloon float altitude, the Earth’s atmosphere
is transparent at some wavelength bands
between 200 and 300 nm. Figure 5 shows the
atmospheric transmission and UV solar
irradiance in the range 185-295 nm at a height
of 40 km and a latitude of S77.9 on Dec.21
(typical of an Antarctic LDB mission.)
Figure 5: Atmospheric UV transmission (upper panel)
and solar irradiance (lower panel) as a function of
wavelength and solar zenith angle (sza). Contours and
color scale are logarithmic. Lighter shades denote higher
transmission or higher flux, respectively. Figure courtesy
of D. Marsh, HAO/NCAR.
These images show that, even on an Antarctic
LDB mission, a balloon-borne solar telescope
will see adequate solar flux for imaging and
spectroscopy at 205 nm and 280 nm. The test
flight should encounter even higher atmosphere
transmission at these wavelengths. Of interest
are the highly transmissive wavelengths around
the Al I ionization edge at 207 nm and in the
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vicinity of the Mg II k (279.6 nm) and Mg I
(285.2 nm) resonance lines.
The wavelengths around the Al I edge probe
the middle photosphere (h  200 km,
Vernazza et al. 1981). The opacity there has
a strong contribution from spectrum lines.
Broadband observations at this wavelength
will be very sensitive to the thermal
structure at heights where the magnetic
diagnostic lines in the visible (i.e. the Fe I
lines at 630 nm) form.
In several regards the Mg II resonance lines
are better suited as chromospheric
diagnostics than the frequently used Ca II
resonance lines near 400 nm:
 The shorter wavelength implies greater
sensitivity to temperature.
 The Mg II resonance lines form higher
in the chromosphere than their Ca II
counterparts.
 Because these lines do not share upper
levels that branch to other strong
transitions (as in the infrared triplet lines
of Ca II), the line transfer in the Mg II
line wings is highly coherent. Thus,
their near wings are suppressed and their
chromospheric emission cores are
prominent. Mg II k-line spectra thus
provide
a
clear
indicator
of
chromospheric structure and dynamics,
and the profile plus its wings sample the
photosphere to the upper chromosphere.
High resolution space instrumentation has
largely shunned the chromosphere: the
important link between the photosphere and
corona. Observations of this region are
essential to explore the magnetic
underpinnings of coronal activity. From the
photosphere to the upper chromosphere the
pressure falls by a factor of 105-106.
Spatially isolated, small flux tubes thus
undergo tremendous expansion through the
chromosphere. MHD waves may undergo a
fundamental change in character while
propagating upward through the chromosphere.
By providing ultra high resolution, quantitative
spectra of the Mg II k-line, Sunrise will fill a
very important observational void in our study
of the heating and dynamics of the upper solar
atmosphere. The freedom from atmospheric
seeing will enable:
 searches for high frequency waves
propagating upward from individual flux
tubes,
 recording the dynamics of sunspot fine
structure, including umbral flashes,
 study of the apparently non- or weaklymagnetic oscillations in the internetwork
regions of very quiet Sun, including effects
of horizontal propagation.
E. Relationship to Other Programs
With the aid of phase diversity image
reconstruction, Sunrise will image the
photosphere at 200 nm and the chromosphere in
the Mg II k resonance line at 280 nm, and will
therefore achieve a spatial resolution of 30 and
40 km on the Sun, respectively. Sunrise will be
able to resolve solar structures a factor of 4 - 6
smaller in linear dimension than Solar-B, thus
both opening a new realm of solar phenomena
to quantitative investigation, and fully resolving
(i.e. critically sampling) structures the size of a
photospheric scale height. Its capability to
perform precision Stokes I spectroscopy in the
UV Mg II resonance lines provides a diagnostic
capability of the chromosphere unavailable to
new large-aperture ground-based telescopes.
With its unique capability, the Sunrise program
augments worldwide efforts to better understand
the small-scale origins of solar variability and
the physics of magnetized plasmas in stellar
atmospheres.
Page 5 of 15

I. Technical Approach
A. Overview
Advantages of a balloon mission over
ground-based observations are freedom from
atmospheric seeing over a large field-ofview and access to the ultraviolet.
Additionally, a two-week LDB mission from
Antarctica would provide continuous
observing of solar phenomena during one
complete disk passage.
The Sunrise instrumentation consists of a
main telescope with an aperture of 1 m
feeding three focal-plane instruments:
 The Spectrograph Polarimeter (SP):
for measurements of all four Stokes
spectral profiles, and precision Stokes I
spectral measurements of ultraviolet
chromospheric line profiles,
 The Imaging Magnetograph (IMaX):
for high resolution, two-dimensional
imaging of the photospheric vector
magnetic field, and

The Filtergraph (FG): for diffractionlimited imaging in selected ultraviolet
and visible light wavelength bands
A correlation tracker controlling a tip-tilt
steering mirror provides image stabilization
and high-precision guiding. An auxiliary
full-disk telescope (FDT) provides both a
fine pointing signal and full-disk images for
interactive target selection.
The German contribution, through the KIS
and MPAe institutions will provide:
 the telescope; including its structure,
secondary mirrors, field stop, heat dump,
and active wavefront control,
 the FDT, its CCD detector, and data
system,
 the SP, exclusive of its CCD detectors
and DPUs,
 the FG instrument and data system,


the correlation tracker (CT), wavefront
control system, and associated control
electronics,
the optics to distribute the light from the 1-m
telescope to its three focal plane
instruments, and
the instrument control and data storage
systems.
The Spanish (IAC) will provide the IMaX.
NASA will provide the lightweight CSiC
primary mirror through prior contracts with
LMSAL. Under this proposal, NASA would
provide:
 the CCD detectors and Data Processing
Units (DPUs) for the SP (HAO), and
 the balloon gondola and its support systems
(power, telemetry, rough and intermediate
pointing) (HAO/NCAR)
B. 1-m Telescope
The clear aperture of the telescope is 1 m and
the parabolic primary mirror (M1) has a focal
length of 2.5 m.
The elliptic Gregorian
secondary mirror (M2) increases the effective
focal length of the system to 25 m (f/25). Figure
6 shows the optical schematic of the main
telescope.
Figure 6: Optical layout of the Sunrise telescope.
A reflective cone of solid copper located at the
prime focus rejects about 99% of the incoming
flux, but admits a circular field of view of
3.4 arcmin (10 W of solar radiation) through a
Page 6 of 15
3 mm central hole. The flat mirrors M3 and
M4 fold the beam so that it is parallel to the
optical axis of the telescope and feeds the
focal-plane package. The tip-tilt steering
mirror M4 is controlled by both the
correlation tracker unit and the guider in the
FDT. It provides precise pointing and
guiding to 0.005 arcsec. Baffles and multilayer insulation (MLI) covering the
telescope structure minimize stray light.
Alignment of the primary and secondary
mirrors is maintained by a Serrurier truss.
The secondary M2 alignment is adjustable in
2 degrees of freedom, and is adjusted
dynamically with error signals from the
correlation tracker/ wavefront sensor.
Thermal control of the telescope is entirely
passive, and the thermal design is greatly
aided by the high thermal conductivity of
the silicon carbide ceramic (C/SiC) mirrors
The primary mirror (M1) radiates the
absorbed energy from its backside. The
field stop at the prime focus is also passively
cooled: heat absorbed by the field stop is
removed by conduction to a radiator
mounted on the instrument structure.
The 45 reflections of M3 and M4 introduce
a constant instrumental polarization which
produces crosstalk among the Stokes
parameters. The degree of crosstalk will be
measured
during
extensive
ground
calibration, so that the polarization data may
be corrected.
This procedure has a
successful
history
in
ground-based
polarimetry.
C. Ceramic Silicon Carbide Mirrors: A
New Astronomical Telescope Technology
The very large stiffness of C/SiC combined
with a moderate coefficient of thermal
expansion makes this material attractive for
light-weight mirrors for space applications.
The high thermal conductivity of the
material makes the cooling of the mirror a
comparatively simple task for solar telescopes.
However, the manufacture of a C/SiC meterclass mirror is a major technological challenge.
The C/SiC material cannot be polished directly.
It needs to be coated with a special slurry made
from Si:SiC. In March, 2001 a mirror of
diameter 36 cm was coated and polished to /10
with a surface roughness of 3 nm.
The Astrium company is developing the C/SiC
technology. Currently, the 1-m mirror for the
Sunrise project (Figure 7) is being
manufactured under separate NASA contract.
Figure 7: The two C/SiC SolarLite mirror blanks, each
1.0 meters in diameter are displayed. One of these blanks
will be used in the Sunrise telescope. The back side of the
blanks have integrated mounting points (courtesy of N.
Pailer, Astrium/Dornier Satellitensysteme.)
D. Pointing and Guiding Systems
A very stable image is crucial to the success of
the proposed investigation. There are several
drivers for Sunrise image stability:
 Diffraction-limited imaging in the
ultraviolet demands that the image be
stable to a fraction of the 0.015 arcsec
pixel size during a typical exposure (2
sec). The target value is 1/10th the
diffraction limit at 200 nm: 0.005 arcsec.
 The visible-light magnetograph must
difference sequential images in order to
construct a magnetogram. Crosstalk
from Stokes I into polarization due to
image motion must be avoided at a level
Page 7 of 15

of 1% or smaller, implying that
residual image motion be less than
0.01 arcsec in the interval between
successive polarimetric samples.
The image must be stable enough to
meet the requirements of spectropolarimetry at the 10-3 level. This
requirement
has
been
wellestablished
for
dual-beam
polarimeters (such as the POLIS
instrument) at 0.01 arcsec.
Image motion from atmospheric turbulence
at an altitude of 30-40 km is negligible
compared to the anticipated resolution limit
of 0.05 arcsec. At that altitude, the payload
drifts with the local winds. It is above 99.5%
of the atmosphere and the turbulence of jet
stream boundaries.
Therefore, local
turbulence even at these low densities is
minimized. These factors suggest that, in
the visible, variations in atmospheric index
of refraction should be at least a factor of
200 smaller than experienced from the
ground under the best (0.2 arcsec) seeing
conditions, resulting in “seeing” at that
altitude of <0.001 arcsec (or <0.003 arcsec
at 200 nm.)
Following the Flare Genesis model
(Bernasconi, et al. 2000), the pointing of the
Sunrise telescope structure will be
controlled by a three-stage system:


Raw pointing in azimuth with an
accuracy of about 2.5 deg using four
photodiode sensors mounted at 90 deg
intervals around the gondola; the
elevation of the Sun is taken from a
calculation of the ephemeris based on
GPS time and position.
Coarse pointing using the azimuth and
elevation signals provided by a LISS
(Lockheed Intermediate Sun Sensor)
with a 14 degree field of view. This twoaxis solar sensor is capable of providing

a pointing reference to the Sun within
10 arcsec.
Fine pointing and tracking with aid of the
fine solar guider, similar to that in use by the
TRACE mission, attached to the FDT. This
guider has ample sensitivity to point the
telescope structure at guiding rates limited
by the telescope azimuth and elevation
motors.
The Flare Genesis experience
demonstrates that pointing of the whole
telescope within 1-2 arcsec may be achieved
in this manner.
Two more stages of image stabilization will be
adopted to reach the goal of 0.005 arcsec
stability. The tip-tilt mirror M4 internal to the
telescope will be used to compensate the
residual motions smaller than 1-2 arcsec. The
residual, high frequency error signal from the
TRACE-like guider (motions not corrected by
pointing the telescope itself) will be used to
generate offset signals for M4. This will
stabilize the image to under 0.2 arcsec. For the
final stage of image stabilization, the CT
internal to the main telescope will generate
offset signals from a scene of solar granulation.
The size of typical solar granules — 1-2 arcsec
— sets the requirement for image stability
(0.2 arcsec) prior to the CT. The CT will
perform the final, high frequency stability of the
image to 0.005 arcsec, i.e. 1/10th the diffraction
limit at 200 nm. The closed-loop bandwidth of
the whole system will be in the range of 50 Hz.
The CT will also compensate for solar rotation.
Temporal averages of the CT motion estimates
will be used as input to the telescope pointing
system to insure that the telescope is always
kept within the dynamic range of the steering
mirror.
The balloon gondola is subject to pendulum-like
motions with angular amplitudes of typically
4 arcmin and a period of a few seconds. This
causes image motion that is easily compensated
Page 8 of 15
by the guiding system, but it also causes
slight image rotation, corresponding to e.g. a
linear displacement at the edge of the 30
arcsec FOV of the imager of 20 km on the
Sun. This rotation is slow enough that it
does not cause significant blurring during
the short exposures of the FG, SP, or IMaX.
Some rotational correction of FG and IMaX
images may be necessary in postobservation analysis.
E. Wavefront Control System
The optical alignment of Sunrise is an
important and critical issue. Based upon
experience available at LMSAL and KIS, a
wave front control system will be
implemented that detects low-order modes
of wavefront deformations by the telescope
mirrors. A wave front sensor with seven
sub-apertures measures the actual state of
the optical alignment and generates
appropriate error signals to drive the lateral
position of the secondary mirror, M2, and
the tip and tilt of mirror M4.
F. Spectrograph Polarimeter
The main science goals of Sunrise demand
quantitative and accurate measurements of
the strength and orientation of the magnetic
field with appropriate resolution: spatial,
spectral, and temporal. The Spectrograph
Polarimeter (SP) combines the power of a
high-resolution Stokes polarimeter having a
polarimetric accuracy of 10-4 with the
versatility of a multi-line Echelle
spectrograph.
This
configuration
simultaneously
provides
photospheric
magnetic field measurements (polarimetric
branch) and diagnostic spectroscopy of
photospheric and chromospheric lines
(diagnostic branch). The SP is based on an
all-mirror Echelle spectrograph in a
modified Littrow configuration. Apart from
the UV capability below 380 nm, the SP
(Figure 8) is nearly identical to the POLIS
instrument which is currently being
developed jointly by KIS and HAO. A detailed
description of that instrument is given by
Schmidt et al. (2001).
The diagnostic branch of the SP measures the
intensity profile of a spectral line that is chosen
from a number of preselected lines using a set of
narrow-band filters mounted on a filter wheel,
including chromospheric lines in common with
the FG.
In particular, the SP permits
spectroscopy of the unique chromospheric
diagnostic Mg II K line core at 279.6 nm.
Many aspects of the data system will be adopted
from POLIS. The CCD cameras for the SP will
be the same PixelVision Pluto cameras in use
with the POLIS system. The data acquisition
and camera control for the SP will be singleboard PC computers. Both the cameras and
computer will be modified to operate using DC
voltage and fit within pressure vessels.
Figure 8: The scheme of the SP and FG. The beam
separator and phase diversity camera for the FG are not
shown. The all-reflecting design permits simultaneous
operation in the visible and UV.
G. Filtergraph
The filtergraph (FG) instrument will be an
important part of the scientific package (Figure
8). It is a simple imager intended to extract the
highest resolution images possible with a 1-m
telescope operating at ultraviolet wavelengths as
small as 200 nm. Its FOV is 3030 arcsec area
centered on the middle of the SP slit. One
possibility for a FG detector is the Solar-B
Page 9 of 15
20484096 thinned, back side illuminated,
CCD fabricated by Marconi. Readout rate is
3 Mpx/sec, resulting in a readout rate of one
frame per 3 sec. Table I summarizes the
capabilities of the SP, FG, and IMaX.
TABLE I
Summary of instrument specifications
Telescope
1 m diameter
2.5 m primary focal length
F/25 effective focal ratio
8.25 arcsec/mm image scale
A beam splitter (not shown in Figure 8)
spatially separates the in- and out-of-focus
images for phase diversity imaging. The
out-of-focus image will be optimized for one
wave of defocus at 205 nm. Phase diversity
correction will be integral to all FG
observations, and will insure that the
sequence of images remain diffractionlimited at each of the observed wavelengths.
Full-disk telescope
1000 mm FL/100 mm dia. (lens)
2048  2048 CCD
10  10 m2 pixel size
TRACE-like limb sensors
Correlation tracker
128  128 CCD Wave front sensor
0.01 arcsec pointing accuracy
 50 Hz dynamic range
Wavefront sensor
7 elements
5 Zernike terms
H. Imaging Magnetograph
Small-scale
solar
phenomena
(i.e.
emergence of magnetic flux) can occur on
size and time scales that are incompatible
with 2D mapping by scanning the SP slit.
The imaging magnetograph IMaX provides
the needed 2D context for the SP
measurements. It is capable of full Stokes
polarimetry sequentially at
selected
wavelengths.
Narrowband wavelength
isolation is accomplished by tuning a system
of Fabry-Perot etalon interferometers (FPIs)
with a wavelength discrimination of about 4
pm. Like the SP, the IMaX system will
operate in a spectrum line located in the
visible or near IR with comparable spatial
sampling and coverage. Modulation of the
polarization will be accomplished via a
liquid crystal variable retarder in a manner
similar to that of two precision spectropolarimeters developed at the IAC and
currently in operation at observatories in the
Canary Islands.
Spectrograph
Scanning unit
1250 mm focal length
0.05 arcsec step width
60 arcsec total range
158 grooves/mm grating
2.7 pm spectral resolution
12.6 pm/mm at 630nm dispersion
Dual beam system
Rotating wave plate at 1 Hz
652  488 format, 15 fr/s
12 12 m2 pixel size
65 arcsec  0.26 nm
630.2 nm (Fe I)
65 arcsec  0.24 nm
20 regions (1.5 - 2 nm wide)
from 270 to 1100 nm
I. Data Storage
The Sunrise instruments produce data at a
high rate, which would be very difficult to
downlink in real time. Therefore, a
substantial on-board data storage capacity is
Main disperser
Polarimetry Unit
CCD-cameras
CCD I FOV
CCD II FOV
Filtergraph
Filter wheel
Magnetograph
2048  4096 CCD
12 12 m2 pixel size
30 30 arcsec2  2 FOV
550 nm (cont.), 388 nm (CN-band)
393 nm (CaII K), 279 nm (MgII k)
285.3 (MgI), 205 nm (continuum)
1024  1024 CCD
12-14 m2 pixel size
102  102 arcsec2 FOV
Series of Fabry Perot etalons
4 pm bandpass
needed in order to decouple the data acquisition
from the limited telemetry rates. Assuming that
the peak rate is reached during 12h per day, the
data collected during a 2-day conventional
balloon flight amount to 60GB, while a 10-day
Page 10 of 15
LDB flight will produce 300GB, at
maximum. The Data Storage System (DSS)
consists of a stack of hard disks with
sufficient shock resistance to withstand the
accelerations during parachute opening
(about 10g) and landing (up to 50g in the
case of landing on solid rock). Commercial
hard disk for laptops like the IBM Travelstar
32GH (32GB, 2.5-inch form factor) are
resistant to shocks of 700g (2ms half sine
wave) in non-operating mode. A stack of 12
such disks will be operated as a pair of
independent RAID-level-4 systems of five
data and one parity disk each, providing
320GB disk space.
angular momentum from the reaction wheel to
the balloon. Most of the electronics is housed in
thermally controlled pressurized vessels at the
bottom of the gondola, along with appropriate
external radiators. The gondola structure is
mounted upon the Support Instrument Package
(SIP) (not shown in Figure 9), which controls
the balloon systems. Apart from an RS-232
interface for telemetry, the SIP is electrically
and thermally isolated from the science systems
and has an independent photovoltaic power
system.
MOMENTUM
TRANSFER
UNIT
GONDOLA
ATTACHMENT
RINGS
SOLAR
PANELS
IV. Balloon Concept
INSTRUMENT
BENCH
A. Gondola frame and telescope mount
The Sunrise telescope is mounted on the
elevation axis to a frame consisting of
standard aluminum components and foamcore composite that offers excellent strength
to weight ratio. NCAR’s Atmospheric
Technology Division (ATD) will design and
assemble this structure and a mechanical
latch to lock the telescope in the horizontal
position for ascent and landing. Mechanical
models will be developed in order to specify
the payload’s frame construction such that
the landing shock load arriving to the
telescope will be minimized from 10/50 G
(parachute shock load/cross wind landing) to
2-3 G when landing on rocky terrain. The
frame is connected to the gondola structure
through support arms that can be adjusted
for latitude and launch vehicle type. The
gondola can be moved in azimuthal
direction to point the telescope and the solar
panels towards the Sun. This is realized by
means of a momentum transfer unit (MTU)
mounted at the top of the gondola (Figure
9). The MTU consists of a motor providing
torque between the frame and a reaction
wheel, together with a second motor acting
as a shorted generator to shift accumulated
ELEVATION
ENCODER
HOUSING
AEROFLEX SHOCK
ABSORBERS
PRESSURE VESSELS, DATA
STORAGE, PROCESSING AND
INSTRUMENT CONTROL
Figure 9: The Sunrise telescope is shown in the balloon
gondola as deployed for observations. During ascent and
landing, the telescope is locked in a horizontal position.
This and retractable covers over the front ring of the
telescope help protect the payload.
To maintain maximum flexibility for the
mission, the entire system will be designed to
meet the most restrictive launch vehicle
requirements (LDB Antarctic launch vehicle)
regarding dimensions, weight etc.
The weight estimate of the scientific payload
assumes that the structure of the main
telescope
consists
of
Carbon-Fibre
Reinforced Plastic. The combined weight of
balloon gondola, telescope frame, MTU, and
the support systems (power, telemetry) are
also of the order of 500 kg, so that the total
mass of the payload remains significantly
Page 11 of 15
below the maximum payload mass of
about 1360 kg for an Antarctic LDB
flight. See Table II.
stability under flight conditions. The rigging
suspension will also be designed to simulate inflight pendulum motion so that all servo
dynamics can be evaluated.
TABLE II
Weight Estimates
Unit
Main telescope
Full disk telescope (FDT)
Filtergraph (FG)
Spectrograph (SP)
Magnetograph (ImaX)
Wave front sensor
Electronics
Contingency
Total weight
Weight
300
30
15
60
20
10
50
60
545
B. Attitude Control Mechanisms
The elevation axis will be mounted on large
four-point contact ball bearings to minimize
damage during landing and to allow for high
radial and axial stiffness with minimal static
and dynamic friction. One brushless D.C.
servomotor will be used for the elevation
drive. It will provide sufficient torque to
insure adequate elevation control response
without the need for a gear reduction
system, thereby eliminating backlash errors.
The balloon/rigging side of the azimuth
bearing structure will be sufficiently stiff to
prevent deflection of the 10-inch, .5 inch
cross section radial contact bearing during
operation. The gondola side of the bearing
structure will provide sufficient torsional
stiffness to minimize servo loop pointing
errors. Two brushless D.C. servomotors will
be used in the azimuth drive; one motor will
be attached directly to the gondola side of
the bearing to apply azimuth control and, the
other motor will rotate a mass in the
opposite direction to counteract the torque of
the first motor.
The servo system will be fully tested prior to
flight.
A simulated payload will be
suspended from a rigging that is identical to
the flight rigging so that all servo parameters
may be adjusted to provide maximum
C. Power system and telemetry
A well-proven power system, developed by
Meer Instruments of San Diego for the Flare
Genesis Experiment, will be duplicated for
Sunrise. The system consists of four elements:
the solar panels, the charge control unit, the
voltage regulators, and the battery stacks. There
are ten solar panels, five on either side of the
gondola, with 9.6 m2 active area and generating
1.3 kW at float altitude. The operating point for
the photovoltaic cells is set by the charge
controller, which administers the power from
the panels and three 1 kWh battery stacks.
The telemetry unit for line of sight (LOS)
communication will have a bandwidth of
0.5 Mbit/s. This will allow interactive
observing as long as the balloon is above the
horizon at the launch site. The LOS unit will
transmit uncompressed pictures from the FDT in
about 2 minutes. Correspondingly shorter
transmission time is required for compressed
images; we expect 10 s transmission time for
full-disk images to be used for raw target
selection.
D. Flight plan
There will be a 1-2 day conventional balloon
test flight out of the NSBF (National Scientific
Ballooning Facility) site at Fort Sumner (New
Mexico) during the stratospheric turnaround
conditions in summer of 2005. This flight will
occur during solar minimum. However, a main
focus of the program is observation of flux
tubes, which are ubiquitously present at all
phases of the solar cycle. Under such
conditions, the balloon can be expected to stay
for up to 50 hours within the LOS, so that full
interactivity of the observations and data
transfer to the ground can be maintained by the
LOS telemetry system.
Page 12 of 15
Long Range: Since the gondola will be
designed around the Antarctica constraints,
Sunrise could be flown in the framework of
NASA's Long Duration Balloon (LDB)
program. We would anticipate a flight of 1012 days in the austral summer 2006-2007
from the ballooning facilities at McMurdo,
Antarctica. The flight trajectory will be
circumpolar, bounded between 72 deg and
83 deg south latitude. Float altitudes would
be 35-40 km. Flying during summer over
Antarctica has the advantage of permanent
sunlight and small elevation changes of the
Sun, so that observation and power
generation
would
be
uninterrupted;
furthermore, the thermal conditions would
not vary significantly and the balloon would
float at nearly constant altitude. These
advantages more than compensate for the
logistical difficulties associated with
campaigns in Antarctica.
E. Flight operation
LOS communication will provide full
interactivity during most of the flight over
New Mexico/Texas. This will be used for
extensive functional tests of the scientific
hardware and the support systems. Upon
successful operation, a first set of scientific
data will be obtained during the test flight.
Data will be reduced and presented in
December 2005.
Command sequences for a large variety of
science experiments are stored in the
onboard Instrument Control Unit (ICU).
These sequences are initiated by simple
commands, which considerably simplifies
the experiment control. For the non-LOS
phase of a LDB flight, the ICU changes to
an autonomous observing mode and runs
predefined experiments either from a fixed
sequence or determined by the results of an
automatic analysis of images from the fulldisk auxiliary telescope (FDT), for example,
when a sunspot group is detected. The
adequacy and the proper operation of the
autonomous observing mode will be checked
and validated during the test flight.
Full-disk images provided by the FDT will be
transmitted to the ground during LOS contact to
allow target selection and pointing.
Fine
pointing with sub-arcsec precision will be done
with the CT. Images from the CT
(128128 pixels) can be transmitted to the
ground at a rate suitable to allow even fine
target selection. Occasional samples of heavilycompressed science data will also be transmitted
to the ground station in order to check the
performance of the instruments.
F. NCAR Ballooning Heritage
NCAR has conducted high-altitude scientific
balloon experiments for nearly 40 years. The
headquarters of the National Scientific Balloon
Facility (NSBF) was first located at NCAR's
Boulder facility, and operations at Palestine,
Texas launch site were performed under
contract by Raven Industries. Eventually, the
operation at Palestine was staffed by NCAR
employees and the facility was operated in that
mode until 1983 when NASA took over NSBF.
Much of the current technology used in modern
ballooning was developed by NCAR. NCAR’s
ATD continues to build and fly experiments on
balloons and high altitude aircraft.
V. MANAGEMENT PLAN
A. Schedule
The main contributions by HAO/NCAR are
depicted in bold. In addition, HAO/NCAR will
develop the camera and acquisition hardware for
the SP. This will be a similar system as one
developed by HAO for POLIS.
Thermal and structural design of the gondola
will involve interactions between ATD and
telescope engineers to ensure that the finalized
instrument package will be an integrated
system. Therefore, time has been heavily
Page 13 of 15
allocated within the first year to address
these issues. See Figure 10.
scientist (PS) will be the point of contact for all
scientific matters. He coordinates the planning
of the science experiments and monitors the
technical development with respect to the
preservation of the science goals.
TABLE III
HAO/NCAR
PI: Bruce Lites
General oversight of US program, flight support,
post-flight science data analysis
CoI: Michael Knölker
Supporting theory and modeling
CoI: Steve Tomczyk
Instrument design
PM: Kim Streander
Management of development of balloon gondola
and SP imaging/data system
LMSAL
CoI: Alan Title
Oversight of FG instrument
CoI: Thomas Berger
Flight support, image analysis, data interpretation
Collab: Bart dePontieu
Data interpretation, modeling
Collab: Karel Schrijver
Mission planning, data interpretation
Collab: Theodore Tarbell
Image stabilization, flight support, data interpretation
NSO
CoI: Christoph Keller
Instrument design, flight support, image analysis
Figure 10: Schedule for the development of
Sunrise.
B. Project Structure
The Sunrise investigation is comprised of
several instruments being built at different
institutions. See Table III. Responsibility for
the design, development, and fabrication of
the individual instruments and subsystems
rests with the respective institutional PI. The
daily project management responsibilities
are delegated to Dr. W. Curdt (MPAe) as
program manager (PM), who will be directly
responsible for tracking costs and schedule
of
the
various
hardware/software
developments and supervise the industry
activities. Dr. M. Schüssler, the project
University of Chicago
Collab: Fausto Cattaneo
Supporting data interpretation, numerical modeling
Collab: Robert Rosner
Supporting data interpretation, numerical modeling
MPAe
CoI: Sami Solanki
PI, German contribution to Sunrise program
CoI: Manfred Schüssler
Sunrise project scientist
KIS
CoI: Wolfgang Schmidt
German liaison for SP, active wavefront control,
image stabilization
IAC
CoI: Valentin Martínez Pillet
PI for Spanish contribution to Sunrise program,
liaison for ImaX magnetograph
Page 14 of 15
An Investigation Working Group, consisting
of the PIs, their institutional project
managers, the PM, and the PS is responsible
for all coordinated work during the
development phase.
approximately six months after the test flight.
This period is deemed necessary to carry out
necessary data calibration.
The hardware responsibility is distributed
among the collaborating institutes. The main
telescope and the spectrograph-polarimeter
will be defined and built by an aerospace
company under the supervision of the MPAe
and
the
KIS
teams,
respectively.
HAO/NCAR will build the SP data
acquisition system, design the gondola
structure, and assist in the integration and
testing of the overall instrument payload.
The final integration of the system will
occur at NCAR’s facilities in Boulder, CO
in preparation for the test flight from
Palestine.
The timing of the flight and its high profile
within the scientific community makes this a
program students will find interesting. We will
leverage on-going programs at NCAR and
UCAR (as co-sponsorship) which focus on
education at the undergraduate, graduate and
post-doctoral levels. These include the
nationally recognized and NSF sponsored
SOARS program and the High Altitude
Observatory's Newkirk Fellows Program.
Through this suite of activities, the benefits
of the Sunrise program will be extended across
the formal education spectrum from upper
elementary through post-graduate, and will also
support web-based informal science education.
C. Status of the International Program
The German agency DLR has funded two
design studies for the development of the
Sunrise telescope (totaling ~US$100K).
These studies are now underway at
MAN/Mainz and Astrium/Friedrichshafen.
At the conclusion of these studies, funding
for the telescope will be requested from the
DLR. Substantial funding for the German
development of science instrumentation for
Sunrise and for scientific work in
preparation for the mission has been
identified by the Max-Planck Society. A
proposal has been submitted from the
Instituto de Astrofisica de Canarias (IAC) to
the Spanish space agency for design phase
study of the magnetograph.
C. Data Policy
The Sunrise program will adhere to an open
data policy, resembling in some respects that
of the TRACE mission. All of the Sunrise
data will be made available on the internet
D. Education/Public Outreach
In addition, if this proposal is selected for
funding, we will apply for additional funding for
Education and Public Outreach (EPO)
activities. Our EPO efforts will focus on several
complementary efforts, including:
 development and integration of supporting
background content on Sunrise science
(solar magnetic fields, radiation, solar
structure) and technology (observations of
the Sun from high altitude balloons) into
the on-going, successful and high leverage
Windows to the Universe web-site project;
 development and testing of supporting
classroom activities (middle school and
high school level) through collaboration
with educational consultants
 professional development for middle and
high school educators on background
science content and activities, guided by
collaborations with nationally recognized
educators.
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