14795( 2) - 19-Jul-2016 12:45:43 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14795 Version: 2 Check-in Time: 19-Jul-2016 12:45:43 STScI Edit Number: 0 Title Observing an artificial meteor: Cassini's entry into the atmosphere of Saturn ------------------------------------------------------------------------------------ Type Cycle GO 24 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Frank Crary University of Colorado at Boulder Y CoI: Dr. Sarah V. Badman Lancaster University N CoI: Prof. John T. Clarke Boston University N CoI: Dr. Scott G. Edgington Jet Propulsion Laboratory N CoI: Dr. Ralph D. Lorenz The Johns Hopkins University Applied N Physics Laboratory CoI: Petrus M Jenniskens NASA Ames Research Center N ------------------------------------------------------------------------------------ Abstract The Cassini spacecraft's mission at Saturn will end after over 13 years in orbit, on September 15th, 2017. The spacecraft will be disposed of by impacting Saturn and its atmospheric entry will be that of an artificial meteor. The resulting bolide will be observable in the far ultraviolet using Hubble Space Telescope's STIS instrument. We propose to observe this event using STIS-FUV MAMA, in TIME-TAG imaging mode. The goal of this observation is to determine the luminous efficiency of hypervelocity impacts on gas giants. Recent observations of meteor flashes on Jupiter could be used to determine the flux and size distribution of meteors in the outer solar system, but only if the luminoius efficiency is known. With a well-known mass (2186 kg) and impact velocity (34.9 km/s), the Cassini impact will provide this information. An additional goal is the validate and improve the existing model of Saturn's atmosphere, between 1 nanobar and a few microbars. This region is of particular interest to the interpretation of aurora observations and to the development of future missions involving atmospheric probes. ------------------------------------------------------------------------------------ Observations Description ------------------------ The Cassini spacecraft's mission at Saturn will end after over 13 years in orbit, on September 15th, 2017. The spacecraft will be disposed of by impacting Saturn and its atmospheric entry will be that of an artificial meteor. The resulting bolide will be observable in the far ultraviolet using Hubble Space Telescope's STIS instrument. We propose to observe this event using STIS-FUV MAMA, in TIME-TAG imaging mode. The goal of this observation is to determine the luminous efficiency of hypervelocity impacts on gas giants. Recent observations of meteor flashes on Jupiter could be used to determine the flux and size distribution of meteors in the outer solar system, but only if the luminoius efficiency is known. With a well-known mass (2186 kg) and impact velocity (34.9 km/s), the Cassini impact will provide this information. An additional goal is the validate and improve the existing model of Saturn's atmosphere, between 1 nanobar and a few microbars. This region is of particular interest to the interpretation of aurora observations and to the development of future missions involving atmospheric probes. 14795( 2) - 19-Jul-2016 12:45:43 - [ 2] ------------------------------------------------------------------------------------ 14795( 2) - 19-Jul-2016 12:45:43 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET Planet Saturn ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS NOT ECL P PARTIAL OF SATURN BY TITAN FROM EARTH, SEP OF SATURN RHEA FROM EARTH GT 10", SEP OF SATURN TITAN FROM EARTH GT 10" ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 0.8 +/- 1 Ephemeris Center: EARTH Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 14795( 2) - 19-Jul-2016 12:45:43 - [ 4] Visit: 01 (Saturn During Cassini Entry) Visit Requirements: BETWEEN 15-SEP-2017:12:00 AND 15-SEP-2017:12:25 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SATURN STIS/FUV TIME-TA 25MAMA MIRROR BUFFER-TIME=100. 1 2500 S -MAMA G (2500 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SATURN 1 STIS/FUV TIME-TA 25MAMA MIRROR none none none none 1 N/A -MAMA G 14795( 2) - 19-Jul-2016 12:45:43 - [ 5] Summary Form for Proposal 14795 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 25MAMA ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=100. ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 15-SEP-2017:12:00 AND 15-SEP-2017:12:25 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names SATURN ------------------------------------------------------------------------------------------------------------------------------------