6023( 0) - 07/18/95 19:24 - [ 1]
PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only
ID: 6023
Version: **********
Check-in Date: **********
1.Proposal Title:
Observation of OH and CI in the Mars/Phobos neutral cloud with FOS
------------------------------------------------------------------------------------
2. Scientific Category 3. Proposal For 4. Cycle
Solar System GO 5
------------------------------------------------------------------------------------
5. Investigators
Contact?
PI: Dr. Philip Matheson University of Southern California
CoI: Donald Shemanksy University of Southern California N
------------------------------------------------------------------------------------
6. Abstract
We will use the FOS/BL instrument to search for neutral emissions from the
planetary/magneto environment of Mars. Neutral OH is observable in the A-X (0,0)
band at 3085 Angstroms. The program consists of 4 orbits, using the the FOS/BL G270H
with C-3 aperture. Interest in the neutral environment of Mars is spurred by
inferences gathered from PHOBOS-2 that Phobos produces prodigious amounts of dust
and OH along its orbit, forming a neutral cloud or torus similar to that associated
with the icy moons of Saturn. It is estimated that Phobos, primarily an icy body
itself, sources 10^23 H_2O molecules s^-1. Water quickly dissociates to OH and
atomic oxygen. The behavior of Phobos may be somewhat comet-like in this respect.
Three orbits will be used to target the FOS along a line of sight through the ansa
of Phobos' orbit to maximize path length, but will exlude Phobos from the field of
view. The fourth orbit will include Phobos in the field of view to possibly observe
source processes. The source process for Phobos neutrals may be similar to those
which produce the recently discovered O2 atmosphere at Europa and possible OH cloud
about that satellite such as the neutral OH cloud discovered by us in the Saturn
magnetosphere near Tethys and Dione. Phobos' composition is germane to
comet/asteroid studies, particularly at present, because of unresolved issues over
the composition of comet P/Shoemaker- Levy-9.
------------------------------------------------------------------------------------
6023( 0) - 07/18/95 19:24 - [ 2]
Observations Description
------------------------
The program consists of two targets: PHOBOS and MARS-PHOBOS-TORUS. Target MARS-
PHOBOS-TORUS defines the orbital ansa of the moon Phobos, 9378 km from Mars'
center. We nominally plan for an observation date of July 14. On that date,
Mars will be at a solar elongation of 64.6 degrees East. The Phobos ansa will
be 7.42 arc seconds from the center of Mars. The observation is to be made
through the dawn ansa. Pointing should be determined by acquiring Phobos.
Phobos will then be observed and then HST should slew to MARS-PHOBOS-TORUS. The
observing configuration for MARS-PHOBOS-TORUS is FOS/BL G270H grating with the
2.0-PAIR-A aperture. Exposure time is 3 orbits. Aperture should be centered on
ansa, with Phobos excluded from the field of view.The observational setup for
target PHOBOS is identical except that Phobos should physically be within the
aperture. Exposure time 1 orbit minus time needed for target acquisition.
Desired signal derives from OH A-X(0,0) band about 3085 A. However, the OH
signal will be severely diluted by off-axis scattering by sunlight reflected
from Mars. Full integration time will be required to obtain adequate signal-to-
background. Estimated flux: Emission probability in the A-X(0,0) band is
g_Lambda=1E-04 photon/sec/molecule. Taking a path length of 10^9cm and density
of 2500 OH cm-3 gives an extended source brightness of 250 rayleighs over the
whole band. The equivalent flux with the C-3 aperture is approximately 2.E-16
ergs cm-2 s-1 ang-1, giving a count rate of ~ .17 counts s-1 diode-1. However,
the signal rate from off-axis scattering of the solar continuum at 7."42 from
Mars is estimated to be 5.9E-15 ergs cm-2 s-1 ang-1 for a background count
rate of 5 c s-1 diode-1. FOS/BL is selected to minimize grating scatter in this
region of the spectrum. Four orbits should give detection. Observation must be
made within the first 8 weeks of cycle 5. Mars comes within 50 degrees solar
elongation on August 25, 1995.
Real Time Justification
-----------------------
Calibration Justification
-------------------------
Additional Comments
-------------------
------------------------------------------------------------------------------------
Data Distribution
Media: 8MM
Blocking Factor: 10
Ship To: PI_Address
Ship Via: UPS
Email: ,
------------------------------------------------------------------------------------
6023( 0) - 07/18/95 19:24 - [ 3]
TARGET LIST b)Solar System Targets
------------------------------------------------------------------------------------------------------------------------------------
TARGET NUMBER: 1 | TARGET NAME: MARS-PHOBOS-TORUS
------------------------------------------------------------------------------------------------------------------------------------
TARGET DESCRIPTION: TORUS MARS
------------------------------------------------------------------------------------------------------------------------------------
TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2
|
STD = MARS | TYPE = TORUS, LONG = 270, LAT = 0, RAD
| = 9400, POLE_LAT = 90
|
------------------------------------------------------------------------------------------------------------------------------------
TARGET POSITION LEVEL 3 | WINDOWS
|
| OLG OF PHOBOS BETWEEN 120 360
|
------------------------------------------------------------------------------------------------------------------------------------
DATA | COMMENTS
|
SURF-LINE(3085) = 2.00 +/- 0.5E-16 | OFF-AXIS solar scattering gives
SURF-CONT-BKG(3085) = 5.9 +/- 0.5 E-15 | large BKG. Phobos should be excluded
W-LINE(3085) = 11.4 +/- 1 | from FOV Note that information on
| large off-axis scattering not
| available at Phase1 deadline.
| Scattering determined by recent
| observations of Europa and Saturn
| magnetosphere.
|
------------------------------------------------------------------------------------------------------------------------------------
TARGET NUMBER: 2 | TARGET NAME: PHOBOS
------------------------------------------------------------------------------------------------------------------------------------
TARGET DESCRIPTION: SATELLITE PHOBOS
------------------------------------------------------------------------------------------------------------------------------------
TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2
|
STD = MARS | STD = PHOBOS
|
------------------------------------------------------------------------------------------------------------------------------------
TARGET POSITION LEVEL 3 | WINDOWS
|
| OLG OF PHOBOS BETWEEN 66 113
|
------------------------------------------------------------------------------------------------------------------------------------
DATA | COMMENTS
|
SURF-LINE(3085) = 2.00 +/- 0.5E-16 | OFF-AXIS solar scattering give rise
SURF-CONT-BKG(3085) = 5.9 +/- 0.5 E-15 | to Large SURF-CONT-BKG. Exposure
W-LINE(3085) = 11.4 +/- 1 | should be made on Dawn side of
| planet with Phobos included inside
| FOV.
|
------------------------------------------------------------------------------------------------------------------------------------
6023( 0) - 07/18/95 19:24 - [ 4]
Visit: 01
Visit Requirements: BETWEEN 01-JUL-95 AND 25-AUG-95
On Hold Comments: <none>
Additional Comments: <none>
Exposures
------------------------------------------------------------------------------------------------------------------------------------
Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
------------------------------------------------------------------------------------------------------------------------------------
1 PHOBOS FOS/BL ACQ/PEA 4.3 G270H SEARCH-SIZE-X=1 1 15S ONBOARD ACQ FOR 2
K SEARCH-SIZE-Y=3
SCAN-STEP-
Y=1.23
------------------------------------------------------------------------------------------------------------------------------------
2 PHOBOS FOS/BL ACQ/PEA 1.0 G270H SEARCH-SIZE-X=6 1 15S ONBOARD ACQ FOR 3-8
K SEARCH-SIZE-Y=2
SCAN-STEP-X=.61
SCAN-STEP-Y=.61
------------------------------------------------------------------------------------------------------------------------------------
3 PHOBOS FOS/BL ACCUM 1.0- G270H 3085 STEP- 1 630S
PAIR-A PATT=SINGLE
------------------------------------------------------------------------------------------------------------------------------------
4 MARS-PHOBOS FOS/BL ACCUM 1.0- G270H 3085 STEP- 1 1830S EXPAND
-TORUS PAIR-A PATT=SINGLE
Comments: In the event that suitable guide stars are
not available, exposures 4-9 may be performed
with single star guiding or even gyro
guiding.
------------------------------------------------------------------------------------------------------------------------------------
5 MARS-PHOBOS FOS/BL ACCUM 1.0- G270H 3085 STEP- 1 1350S EXPAND
-TORUS PAIR-A PATT=SINGLE
------------------------------------------------------------------------------------------------------------------------------------
6 MARS-PHOBOS FOS/BL ACCUM 1.0- G270H 3085 STEP- 1 600S EXPAND
-TORUS PAIR-A PATT=SINGLE
------------------------------------------------------------------------------------------------------------------------------------
7 MARS-PHOBOS FOS/BL ACCUM 1.0- G270H 3085 STEP- 1 1350S EXPAND
-TORUS PAIR-A PATT=SINGLE
------------------------------------------------------------------------------------------------------------------------------------
8 MARS-PHOBOS FOS/BL ACCUM 1.0- G270H 3085 STEP- 1 600S EXPAND
-TORUS PAIR-A PATT=SINGLE
------------------------------------------------------------------------------------------------------------------------------------
6023( 0) - 07/18/95 19:24 - [ 5]
Summary Form for Proposal 6023
Item Used in this proposal
------------------------------------------------------------------------------------------------------------------------------------
Configurations FOS/BL
------------------------------------------------------------------------------------------------------------------------------------
Opmodes ACQ/PEAK ACCUM
------------------------------------------------------------------------------------------------------------------------------------
Optional Parameters SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SCAN-STEP-Y=1.23 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 SCAN-STEP-X=.61
SCAN-STEP-Y=.61 STEP-PATT=SINGLE
------------------------------------------------------------------------------------------------------------------------------------
Proposal Category GO
------------------------------------------------------------------------------------------------------------------------------------
Scientific Category Solar System
------------------------------------------------------------------------------------------------------------------------------------
Special Requirements BETWEEN 01-JUL-95 AND 25-AUG-95 ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3-8 EXPAND
------------------------------------------------------------------------------------------------------------------------------------
Spectral Elements G270H
------------------------------------------------------------------------------------------------------------------------------------
Target Names PHOBOS MARS-PHOBOS-TORUS
------------------------------------------------------------------------------------------------------------------------------------