8658( 25) - 07/15/03 15:53 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8658 Version: 25 Check-in Date: 15-Jul-2003 15:50:59 1.Proposal Title: Atmospheric Escape and the D/H Ratio in Mars' Atmosphere ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: John T. Clarke University of Michigan CoI: Dr. Jean-Loup Bertaux Service d'Aeronomie du CNRS N CoI: Dr. Tobias Owen University of Hawaii N CoI: Dr. Andrew Nagy University of Michigan N ------------------------------------------------------------------------------------ 5. Abstract The highly extended upper atmosphere and the UV airglow of Mars have not been studied by any in situ spacecraft since Mariner 9 in 1972. At the same time, one of the main elements of NASA's space science program today is the study of Mars and how it has evolved over time to a hostile environment, compared with the favorable conditions on the Earth. The availability of long aperture spatially resolved UV spectra with STIS makes it possible to obtain unique information on the extended upper atmosphere of Mars by mapping the H and O dayglow emissions with altitude above the limb. We propose to make these observations just before Mars opposition near the end of HST cycle 9. Initial modeling indicates that we will have sufficient angular resolution and sensitivity to measure the scale heights of the suprathermal atom populations of H and O atoms. We also propose to determine accurate values for the D and H columns, and the D/H ratio, in the upper atmosphere of Mars. The present-day D/H ratio gives vital information leading to understanding the evolution of Mars' atmosphere, the historic escape of water into space, and potentially the remaining water abundance on Mars. ------------------------------------------------------------------------------------ 8658( 25) - 07/15/03 15:53 - [ 2] Observations Description ------------------------ The availability of the sky apertures with the STIS echelle, and in general the use of the STIS, provides an exciting capability to expand our understanding of atmospheric escape and the H and D populations of the upper atmosphere of Mars. Unfortunately the D Ly-alpha emission measured with GHRS at 30 Rayleigh for Mars remains a marginal detection, being at twice the average noise (2Sigma signal). However, it compares quite favorably with the 300 R upper limit that we could derive with IUE on Venus and shows the high potential of HST. The main limitation for this kind of observation remains the scattered light from the grating. For these measurements obtained during Cycle 1, the observing conditions were not optimal, because the data were taken when the HST spacecraft was on the dayside of the Earth, yielding a high geocoronal Ly-alpha emission of about 25 kR and a corresponding high scattered light. In the future, using the STIS, observations could be planned close to opposition. Near opposition in May 2001, the geocoronal intensity will be much lower (roughly 3 kR), and just before or after opposition we can still observe in Earth shadow while having a substantial Doppler shift of the Mars H and D lines from the terrestrial lines from the Earth orbit line of sight velocity. When this Doppler shift exceeds the STIS resolution of 0.057 Angstrom, or exceeds 14 km/sec, the lines will be clearly separated for an unambiguous interpretation. The best time for this observation will be around 10 May 2001, when the Mars diameter will be 15 " at a distance of 0.59 AU from Earth, and the Earth orbital motion along the line of sight will be 21 km/sec toward Mars. The Mars lines will then be blue-shifted with respect to the terrestrial lines, placing the Martian D line farther away from the contaminating geocoronal Ly-alpha line. We propose 5 orbits for this program, to observe the altitude distributions of suprathermal H and O atoms in the upper atmosphere of Mars, and to determine the D and H columns and D/H ratio in the upper atmosphere of Mars. The proposed orbits are as follows: - one orbit for deep 25MAMA and F25SRF2 images, the difference of which will provide the most sensitive measurement of the spatial and altitude profiles of the Ly- alpha emission in Mars' upper atmosphere, mainly the H emission but showing also the D line limb brightening - one orbit for sensitive G140L sky aperture spectra going roughly E/W across the Martian disk, to determine in part the FUV albedo to aid in the scaling and differencing of the two images, and also in part to isolate the altitude profiles of the H and O emission lines - three orbits for sensitive E140H sky aperture spectra going roughly E/W across the Martian disk, to determine the D and H brightnesses and also the all- important emission profiles near the limbs of the planet for modeling of the optical depths and column abundances. From a cycle 7 program for observations of Jupiter, we have initial G140L 52x0.2 and 52x0.5 aperture spectra as well as STIS E140H spectra with the 52x0.5 " aperture, including some regions on the sky background. From these we can estimate the resolution and sensitivity of these observing modes. The efficiency of STIS in both low resolution and echelle modes is similar to that of the GHRS, so that the count rates scale nearly as the aperture area compared with the GHRS LSA. For these observations of extended Mars Ly-alpha emission (in the Earth's shadow the oxygen airglow is too faint to detect), we expect little complication from order overlap in the echelle spectra. We will also have background-free detections of the OI 1304, 1356 Angstrom emission from Mars in both the G140L and E140H spectra, which were not simultaneously obtained by GHRS. For observations of diffuse emission with E140H, the 52x0.5 8658( 25) - 07/15/03 15:53 - [ 3] aperture covering the 15 " Mars disk will give a factor of 1.7 times higher count rate compared with GHRS, with a total aperture length of 25" limited by the MAMA detector size. We expect to confidently detect a 20 Rayleigh D Ly- alpha line in three HST orbits, including the spectral separation of the terrestrial and Mars lines. In the echelle mode E140H, the corresponding FWHM resolution for diffuse emission will be 0.057 Angstrom, giving the STIS 30 percent higher spectral resolution than the existing GHRS LSA spectra. The corresponding STIS resolution with G140L and 52x0.2 aperture is a modest 48 Angstrom, but this is sufficient to determine the spatial distributions of the H and O line emissions across the aperture, as well as the broad-band continuum at longer wavelengths. The known count rate for STIS G140L for the H and O lines is 2.4 cts/sec-kR per 1 " area. For the desired resolution element of 0.1 by 2 " along the 52x2 aperture, we would have 0.48 cts/sec-kR. In one orbit, for a 2400 sec integration, this would give 1150 cts/kr per aperture location, or a 5 sigma limiting sensitivity of 20 Rayleighs. This compares very well with the expected brightnesses in Figure 1. The detector flat field and echelle wavelength calibrations will be available, and in the spectrum of Mars there is little continuum within a couple of hundred Angstrom of the Ly-alpha line so that order overlap will not be a problem using the long aperture and E140H. We can use wavelength lamp spectra with the same aperture/grating to calibrate our spectra during Earth occultation. The observations will be performed with the long aperture aligned roughly E/W across Mars, within the normal off-nominal roll constraints of HST, and blind pointing will be sufficient since we will see the limb of Mars in the spectra. The PI, John T. Clarke has experience observing with HST and STIS, and he will prepare the detailed observing plan and supervise the data reduction and analysis. Co-I J.-L. Bertaux will provide the photochemical modeling. Co-I T. Owen is expert on the science of D and H concentrations and histories in the terrestrial planet atmospheres. Co-I A. Nagy is expert on the modeling of thermal and suprathermal components of H and O atoms in the upper atmospheres of Venus and Mars. Real Time Justification ----------------------- We request observations of Mars shortly before opposition near 10 May 2001, when the Earth's line of sight velocity is roughly 21 km/sec toward Mars and the Mars disk subtends 15". This large apparent disk will provide us with a high sensitivity and also high altitude resolution, with 0.08" = 34 km on Mars. At the same time, the 25" MAMA diameter will allow us to easily observe the sky background at the same time as Mars itself. Observations are also requested in Earth shadow, which is easiest to accomplish when the planet is near opposition. While these observations are not intended to be performed simultaneously with any other NASA missions, the scientific results will be highly complementary to the several NASA missions to Mars in the near future. Of particular relevance will be any information that we can obtain about the density structure with altitude of Mars' upper atmosphere, since Mars Global Surveyor and two other near-term missions will circularize their orbits by air- braking in Mars' atmosphere. Calibration Justification ------------------------- 8658( 25) - 07/15/03 15:53 - [ 4] Additional Comments ------------------- ------------------------------------------------------------------------------------ 8658( 25) - 07/15/03 15:53 - [ 5] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: MARS-1 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET MARS ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=MARS | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = -1.7+/-0.5 | Long-aperture spectra centered on F-LINE(1400)=3+/-1e-14 | Mars, w/roll angle to place aperture W-LINE(1400)=120 | close to E/W across disk F-CONT(1800)=1+/-5e-13 | | Ephemeris Uncertainty: 20000 KM | Acquisition Uncertainty: 10 " | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: MARS-2 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET MARS ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=MARS | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | OLG OF MARS BETWEEN 340 20 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = -1.7+/-0.5 | Images and long-aperture spectra F-LINE(1400)=3+/-1e-14 | centered on Mars, w/roll angle to W-LINE(1400)=120 | place aperture close to E/W across F-CONT(1800)=1+/-5e-13 | disk | Ephemeris Uncertainty: 20000 KM | Acquisition Uncertainty: 10 " | ------------------------------------------------------------------------------------------------------------------------------------ 8658( 25) - 07/15/03 15:53 - [ 6] Visit: 01 Visit Priority: Visit Requirements: ORIENT 283D TO 293D BETWEEN 05-May-2001:08:30:00.0 AND 05-May- 2001:09:30:00.0 BETWEEN 06-May-2001:08:30:00.0 AND 06-May-2001:09:30:00.0 BETWEEN 07-May-2001:08:30:00.0 AND 07-May-2001:09:30:00.0 BETWEEN 08-May- 2001:07:00:00.0 AND 08-May-2001:08:00:00.0 BETWEEN 09-May-2001:07:00:00.0 AND 09-May-2001:08:00:00.0 BETWEEN 10-May-2001:07:00:00.0 AND 10-May- 2001:08:00:00.0 BETWEEN 11-May-2001:05:30:00.0 AND 11-May-2001:06:30:00.0 BETWEEN 12-May-2001:05:30:00.0 AND 12-May-2001:06:30:00.0 BETWEEN 13-May- 2001:05:45:00.0 AND 13-May-2001:06:45:00.0 BETWEEN 14-May-2001:04:15:00.0 AND 14-May-2001:05:15:00.0 On Hold Comments: Additional Comments: Observe Mars in closely scheduled STIS/MAMA orbits, and please schedule as close as possible to 10-MAY-2001. Set HST roll angle set to place STIS long apertures as close as possible to N/S across the Mars disk (set ORIENT to 288D if possible). Last, pls. schedule when STIS MAMA's are cool and dark counts low. BETWEENS restrict observations to be near 2001 Mars opposition and futher restrict observations to take place in the first orbit after an SAA passage. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 MARS-1 STIS/F TIME-TA 52X0.5 E140H 1234 BUFFER-TIME=3000.,WAVECAL=NO 1 1600 S SEQ 11-12 NON-INT REQ UV-MAM G EPHEM CORR MARS01 A ------------------------------------------------------------------------------------------------------------------------------------ 12 MARS-1 STIS/F TIME-TA 52X0.5 E140H 1234 BUFFER-TIME=3000. 1 810 S REQ EPHEM CORR MARS01 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8658( 25) - 07/15/03 15:53 - [ 7] Visit: 02 Visit Priority: Visit Requirements: ORIENT 283D TO 293D BETWEEN 05-May-2001:08:30:00.0 AND 05-May- 2001:09:30:00.0 BETWEEN 06-May-2001:08:30:00.0 AND 06-May-2001:09:30:00.0 BETWEEN 07-May-2001:08:30:00.0 AND 07-May-2001:09:30:00.0 BETWEEN 08-May- 2001:07:00:00.0 AND 08-May-2001:08:00:00.0 BETWEEN 09-May-2001:07:00:00.0 AND 09-May-2001:08:00:00.0 BETWEEN 10-May-2001:07:00:00.0 AND 10-May- 2001:08:00:00.0 BETWEEN 11-May-2001:05:30:00.0 AND 11-May-2001:06:30:00.0 BETWEEN 12-May-2001:05:30:00.0 AND 12-May-2001:06:30:00.0 BETWEEN 13-May- 2001:05:45:00.0 AND 13-May-2001:06:45:00.0 BETWEEN 14-May-2001:04:15:00.0 AND 14-May-2001:05:15:00.0 On Hold Comments: Additional Comments: Observe Mars in closely scheduled STIS/MAMA orbits, and please schedule as close as possible to 10-MAY-2001. Set HST roll angle set to place STIS long apertures as close as possible to N/S across the Mars disk (set ORIENT to 288D if possible). Last, pls. schedule when STIS MAMA's are cool and dark counts low. BETWEENS restrict observations to be near 2001 Mars opposition and futher restrict observations to take place in the first orbit after an SAA passage. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 21 MARS-1 STIS/F TIME-TA 52X0.5 E140H 1234 BUFFER-TIME=3000.,WAVECAL=NO 1 1600 S SEQ 21-22 NON-INT REQ UV-MAM G EPHEM CORR MARS02 A ------------------------------------------------------------------------------------------------------------------------------------ 22 MARS-1 STIS/F TIME-TA 52X0.5 E140H 1234 BUFFER-TIME=3000. 1 810 S REQ EPHEM CORR MARS02 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8658( 25) - 07/15/03 15:53 - [ 8] Visit: 03 Visit Priority: Visit Requirements: ORIENT 283D TO 293D BETWEEN 05-May-2001:08:30:00.0 AND 05-May- 2001:09:30:00.0 BETWEEN 06-May-2001:08:30:00.0 AND 06-May-2001:09:30:00.0 BETWEEN 07-May-2001:08:30:00.0 AND 07-May-2001:09:30:00.0 BETWEEN 08-May- 2001:07:00:00.0 AND 08-May-2001:08:00:00.0 BETWEEN 09-May-2001:07:00:00.0 AND 09-May-2001:08:00:00.0 BETWEEN 10-May-2001:07:00:00.0 AND 10-May- 2001:08:00:00.0 BETWEEN 11-May-2001:05:30:00.0 AND 11-May-2001:06:30:00.0 BETWEEN 12-May-2001:05:30:00.0 AND 12-May-2001:06:30:00.0 BETWEEN 13-May- 2001:05:45:00.0 AND 13-May-2001:06:45:00.0 BETWEEN 14-May-2001:04:15:00.0 AND 14-May-2001:05:15:00.0 On Hold Comments: Additional Comments: Observe Mars in closely scheduled STIS/MAMA orbits, and please schedule as close as possible to 10-MAY-2001. Set HST roll angle set to place STIS long apertures as close as possible to N/S across the Mars disk (set ORIENT to 288D if possible). Last, pls. schedule when STIS MAMA's are cool and dark counts low. BETWEENS restrict observations to be near 2001 Mars opposition and futher restrict observations to take place in the first orbit after an SAA passage. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 31 MARS-1 STIS/F TIME-TA 52X0.5 E140H 1234 BUFFER-TIME=3000.,WAVECAL=NO 1 1600 S SEQ 31-32 NON-INT REQ UV-MAM G EPHEM CORR MARS03 A ------------------------------------------------------------------------------------------------------------------------------------ 32 MARS-1 STIS/F TIME-TA 52X0.5 E140H 1234 BUFFER-TIME=3000. 1 810 S REQ EPHEM CORR MARS03 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8658( 25) - 07/15/03 15:53 - [ 9] Visit: 04 Visit Priority: Visit Requirements: ORIENT 94D TO 114D ON HOLD ORIENT 274D TO 294D BETWEEN 30-Jun-2003 AND 10- Aug-2003 BETWEEN 15-Sep-2003 AND 01-Nov-2003 On Hold Comments: This visit cannot take place as planned during the 2001 Mars opposition due to background bright object concerns. This visit will be replanned for another time. Additional Comments: Set HST roll angle set to place STIS long apertures as close as possible to N/S across the Mars disk (set ORIENT to 104D if possible). Observations should take place in the first orbit after an SAA passage. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 41 MARS-2 STIS/F ACCUM 25MAMA MIRROR 3 338 S REQ EPHEM CORR MARS04 POS UV-MAM TARG 0, 9 GS ACQ SCENARIO A SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 42 MARS-2 STIS/F TIME-TA F25SRF2 MIRROR BUFFER-TIME=400. 1 20 M REQ EPHEM CORR MARS04 UV-MAM G SAME POS AS 41 A ------------------------------------------------------------------------------------------------------------------------------------ 51 MARS-2 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=840,WAVECAL=NO 1 28 M REQ EPHEM CORR MARS04 UV-MAM G SAME POS AS 41 A ------------------------------------------------------------------------------------------------------------------------------------ 52 MARS-2 STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=350 1 700 S REQ EPHEM CORR MARS04 UV-MAM G SAME POS AS 41 A ------------------------------------------------------------------------------------------------------------------------------------ 8658( 25) - 07/15/03 15:53 - [ 10] Summary Form for Proposal 8658 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.5 25MAMA F25SRF2 52X2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TIME-TAG ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=3000. WAVECAL=NO BUFFER-TIME=400. BUFFER-TIME=840 BUFFER-TIME=350 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 283D TO 293D BETWEEN 05-May-2001 08 30 00.0 AND 05-May-2001 09 30 00.0 BETWEEN 06-May-2001 08 30 00.0 AND 06-May-2001 09 30 00.0 BETWEEN 07-May-2001 08 30 00.0 AND 07-May-2001 09 30 00.0 BETWEEN 08-May-2001 07 00 00.0 AND 08-May-2001 08 00 00.0 BETWEEN 09-May-2001 07 00 00.0 AND 09-May-2001 08 00 00.0 BETWEEN 10-May-2001 07 00 00.0 AND 10-May-2001 08 00 00.0 BETWEEN 11-May-2001 05 30 00.0 AND 11-May-2001 06 30 00.0 BETWEEN 12-May-2001 05 30 00.0 AND 12-May-2001 06 30 00.0 BETWEEN 13-May-2001 05 45 00.0 AND 13-May-2001 06 45 00.0 BETWEEN 14-May-2001 04 15 00.0 AND 14-May-2001 05 15 00.0 SEQ 11-12 NON-INT REQ EPHEM CORR MARS01 REQ EPHEM CORR MARS01 ORIENT 283D TO 293D BETWEEN 05-May-2001 08 30 00.0 AND 05-May-2001 09 30 00.0 BETWEEN 06-May-2001 08 30 00.0 AND 06-May-2001 09 30 00.0 BETWEEN 07-May-2001 08 30 00.0 AND 07-May-2001 09 30 00.0 BETWEEN 08-May-2001 07 00 00.0 AND 08-May-2001 08 00 00.0 BETWEEN 09-May-2001 07 00 00.0 AND 09-May-2001 08 00 00.0 BETWEEN 10-May-2001 07 00 00.0 AND 10-May-2001 08 00 00.0 BETWEEN 11-May-2001 05 30 00.0 AND 11-May-2001 06 30 00.0 BETWEEN 12-May-2001 05 30 00.0 AND 12-May-2001 06 30 00.0 BETWEEN 13-May-2001 05 45 00.0 AND 13-May-2001 06 45 00.0 BETWEEN 14-May-2001 04 15 00.0 AND 14-May-2001 05 15 00.0 SEQ 21-22 NON-INT REQ EPHEM CORR MARS02 REQ EPHEM CORR MARS02 ORIENT 283D TO 293D BETWEEN 05-May-2001 08 30 00.0 AND 05-May-2001 09 30 00.0 BETWEEN 06-May-2001 08 30 00.0 AND 06-May-2001 09 30 00.0 BETWEEN 07-May-2001 08 30 00.0 AND 07-May-2001 09 30 00.0 BETWEEN 08-May-2001 07 00 00.0 AND 08-May-2001 08 00 00.0 BETWEEN 09-May-2001 07 00 00.0 AND 09-May-2001 08 00 00.0 BETWEEN 10-May-2001 07 00 00.0 AND 10-May-2001 08 00 00.0 BETWEEN 11-May-2001 05 30 00.0 AND 11-May-2001 06 30 00.0 BETWEEN 12-May-2001 05 30 00.0 AND 12-May-2001 06 30 00.0 BETWEEN 13-May-2001 05 45 00.0 AND 13-May-2001 06 45 00.0 BETWEEN 14-May-2001 04 15 00.0 AND 14-May-2001 05 15 00.0 SEQ 31-32 NON-INT REQ EPHEM CORR MARS03 REQ EPHEM CORR MARS03 ORIENT 94D TO 114D ON HOLD ORIENT 274D TO 294D BETWEEN 30-Jun-2003 AND 10-Aug-2003 BETWEEN 15-Sep-2003 AND 01-Nov-2003 REQ EPHEM CORR MARS04 POS TARG 0, 9 GS ACQ SCENARIO SINGLE REQ EPHEM CORR MARS04 SAME POS AS 41 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E140H MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names MARS-1 MARS-2 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1234 1425 ------------------------------------------------------------------------------------------------------------------------------------