7176( 4) - 08/26/97 09:39 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7176 Version: 4 Check-in Date: 26-Aug-1997 09:38:57 1.Proposal Title: SEARCH FOR A DUST RING AROUND MARS ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle SOLAR SYSTEM GTO/NIC 7 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: BRADFORD A. SMITH INSTITUTE FOR ASTRONOMY CoI: ROLAND MEIER UNIVERSITY OF HAWAII N ------------------------------------------------------------------------------------ 6. Abstract Speculation has long held that a ring of dust particles, sputtered off the dusty surfaces of Phobos and Deimos, must lie in the equatorial plane of Mars. The Earth will pass through the Mars equatorial plane on 2 November 1997. However, because the 50D sun-angle constraint is reached on 14 October, the Earth will be 7D out of the equatorial plane of Mars at the time of the observation. No other opportunities exist within the expected lifetime of NICMOS, so we will attempt the observation in October 1997, with the hope that it can be carried out as late as possible. Three spectral regions are selected to characterize the spectrophotometric properties of the dust and compare them with those of Phobos and Deimos. One lies in the CO_2 absorption band, which will help suppress scattered light from Mars. ------------------------------------------------------------------------------------ 7176( 4) - 08/26/97 09:39 - [ 2] Observations Description ------------------------ The "TORUS" level_2 target is a position in the eqatorial plane of Mars which, when placed at the center of the NIC2 FOV, will put the entire disk of Mars just outside the FOV. Window constraints keep the satellites Phobos and Deimos outside the FOV. LON = 90 is used to observe the West side of Mars as seen from Earth. If the Window constraints should significantly favor the East side of Mars, LON = 270 should be used. However, note that there is a strong scientific driver for favoring the West side (see Additional_Comments). Observations are taken through three filters to get the color of the ring, should one be detected. The F207M filter, which takes up much of the observing time, contains CO_2 absorption bands which should suppress the scattered light from the planet. Real Time Justification ----------------------- Must be scheduled as close to the sun-angle constraint as possible. This occurs near 0000 UT on 14 October 1997. Earlier dates will put the Earth farther out of the Mars equatorial plane and make detection of the hypothetical ring more difficult. Calibration Justification ------------------------- Additional Comments ------------------- We prefer to look at the sunward side of Mars, i.e. on the Western side of Mars as seen from the Earth, to reduce the risk of a large part of the ring falling within the shadow of Mars. However, satellite avoidance is at least as important here, and if for scheduling reasons the Western side is too restricted, the Eastern side is an acceptable alternative. It is important to schedule the visit as late as possible so as to minimize the planetocentric latitude of the Earth, which does not become 0D until 2 November 1997. This means the observation should be scheduled as close as possible to 14 October 1997 0000 UT. The minimal distance between the aperture and the Martian disk is 1.5". IMPORTANT NOTE ============== We chose a chop direction that is tilted by 30 degrees relative to the vertical of the martian equatorial plane. Therefore the chop throw of 1.4" moves the aperture by 0.7" closer to Mars and by 1.2" perpendicular to the equatorial plane. The position angle PATTERN-ORIENT = 155 is set for the WEST, i.e. default side. If LONG = 90 is changed to LONG = 270 (East side) then PATTERN-ORIENT *HAS* to be changed from 155D to PATTERN-ORIENT = 335. ------------------------------------------------------------------------------------ 7176( 4) - 08/26/97 09:39 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Rodger I. Thompson*University of Arizona*Steward Obs./NICMOS*933 N. Cherry Ave*Tucson, AZ 85721-0065 Ship Via: Email: thompson@as.arizona.edu ------------------------------------------------------------------------------------ 7176( 4) - 08/26/97 09:39 - [ 4] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: MARS-RING ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: RING MARS ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=MARS | TYPE=TORUS,LONG=90,LAT=0,RAD=19330,POLE_ | LAT=+90 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | SEP OF PHOBOS MARS-RING FROM EARTH GT | 10.0", SEP OF DEIMOS MARS-RING FROM | EARTH GT 10.0" | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | H = +20.0+/-5.0 | Centered 14.1 arcsec from Mars at PA | = 305D (WEST) or 125D (EAST) | depending on satellite avoidance. | Note that the WEST side is | preferred, because of shadowing of | ring particles by the planet. Mars | radius is 2.55 arcsec. Scale is 1335 | km/arcsec. | ------------------------------------------------------------------------------------------------------------------------------------ 7176( 4) - 08/26/97 09:39 - [ 5] Visit: 01 Visit Requirements: BETWEEN 10-OCT-97 AND 14-OCT-97 ORIENT 95D TO 95D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MARS-RING NIC2 MULTIAC NIC2-FI F207M 2.07500 PATTERN = ONE-CHOP,NUM-POS = 2 , 22 DEF CUM X CHOP-SIZE = 1.40,PATTERN-ORIENT = 155,SAMP-SEQ = STEP32,NSAMP = 8 Comments: Chop throw moves aperture by 1.4" at an angle of 15D relative to the Y-direction of the detector towards Mars. ------------------------------------------------------------------------------------------------------------------------------------ 2 MARS-RING NIC2 MULTIAC NIC2-FI F110W 1.10000 PATTERN = ONE-CHOP,NUM-POS = 2 , 2 DEF CUM X CHOP-SIZE = 1.40,PATTERN-ORIENT = 155,SAMP-SEQ = STEP32,NSAMP = 8 Comments: Chop throw moves aperture by 1.4" at an angle of 15D relative to the Y-direction of the detector towards Mars. ------------------------------------------------------------------------------------------------------------------------------------ 3 MARS-RING NIC2 MULTIAC NIC2-FI F160W 1.60000 PATTERN = ONE-CHOP,NUM-POS = 2 , 3 DEF CUM X CHOP-SIZE =1.40,PATTERN-ORIENT = 155,SAMP-SEQ = STEP32,NSAMP = 8 Comments: Chop throw moves aperture by 1.4" at an angle of 15D relative to the Y-direction of the detector towards Mars. ------------------------------------------------------------------------------------------------------------------------------------ 4 DARK NIC2 MULTIAC NIC2-FI BLANK SAMP-SEQ = STEP32,NSAMP = 8 22 DEF CUM X ------------------------------------------------------------------------------------------------------------------------------------ 7176( 4) - 08/26/97 09:39 - [ 6] Summary Form for Proposal 7176 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations NIC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters PATTERN = ONE-CHOP NUM-POS = 2 CHOP-SIZE = 1.40 PATTERN-ORIENT = 155 SAMP-SEQ = STEP32 NSAMP = 8 CHOP-SIZE =1.40 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GTO/NIC ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 10-OCT-97 AND 14-OCT-97 ORIENT 95D TO 95D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F207M F110W F160W BLANK ------------------------------------------------------------------------------------------------------------------------------------ Target Names MARS-RING DARK ------------------------------------------------------------------------------------------------------------------------------------