17737( 6) - 04-Oct-2024 12:21:25 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17737 Version: 6 Check-in Time: 04-Oct-2024 12:21:25 STScI Edit Number: 2 Title Seasonal dependence of Uranus' upper atmosphere: Tapping 26 years of HST Ly-alpha observations ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Lorenz Roth Royal Institute of Technology Y CoI: Dr. Laurent Lamy Observatoire de Paris - Section de Meudon N CoI: Dr. G. Randall Gladstone Southwest Research Institute N CoI: Dr. Darrell F. Strobel The Johns Hopkins University N CoI: Dr. Nickolay Ivchenko Royal Institute of Technology N CoI: Dr. Henrik Melin Northumbria University N CoI: Mr. Sushen Pravin Joshi Royal Institute of Technology N ------------------------------------------------------------------------------------ Abstract The upper atmospheres of giant planets play key role in various processes such as solar wind interaction, atmospheric escape, magnetosphere-ionosphere coupling, and interaction with ring particles. Voyager2 revealed a largely extended upper atmosphere of Uranus, devoid of hydrocarbons - unique among the solar system's giant planets. It is not yet well understood how the upper atmosphere varies seasonally and Uranus' orbital period of 84 years makes it generally difficult to obtain observational evidence for seasonal changes. However, IR monitoring of ionospheric H3+ emissions suggest a decrease in temperature of the ionized upper atmosphere since 1992. The abundance of H, H2 and H3+ in the upper atmosphere are strongly coupled and indeed HST Ly-alpha observations before (1998) and close to equinox (2011) revealed a similar trend with shrinking and decreasing emissions. Imaging the H Ly-alpha emissions from Uranus with STIS now in cycle 32 - more than a decade after equinox - offers the unique possibility to test the puzzling cooling trend. The new STIS Ly-alpha images together with the archived STIS images will determine if Uranus' neutral upper atmosphere is indeed undergoing continuous cooling. Additional STIS G140M slit spectra provide precise measurements of Raman shifted features for a characterization of the H2 component. With only 8 orbits in 2024 this program will complete a unique archive of FUV data on the only ice giant planet with Ly-alpha emission signal observable from Earth and inform a possible large Uranus Orbiter and Probe mission as recommended by the NASA decadal survey. ------------------------------------------------------------------------------------ Observations Description ------------------------ The idea is to take different kind of imaging and spectral observations combined in one visit to compare the signals and calibrate archival observations of similar type (but never simultanously taken). First we want a global image of only Lyman-alpha emissions through slit-less spectral imaging with G140L and the FUV-MAMA Then we take a long-slit spectrum to get Raman-shifted Lyman-alpha photons longward of the Lyman-alpha line. And finally, we take an image pair with the clear filter (FUV-MAMA) and the S25SRF2 filter. The difference of these two should also give a Lyman-alpha 17737( 6) - 04-Oct-2024 12:21:25 - [ 2] image but with some uncertainty from the throughput dependncy. For our two visits these filter pairs can be calibrated for the first time with the G140L Lyman-alpha image. We do not do acquisitions for the spectral observations. For the slitless exposure exact pointing is not required at all. For the long-slit exposures with the 0.5 arcec slit, even with an offset of up to 1 arcec along x the slit will still intersect with a good fraction of the Uranus' 3.6 arcsec wide disk. One of the visits should optimally happen simultaneously to the observations by JWST from program 5073. ------------------------------------------------------------------------------------ 17737( 6) - 04-Oct-2024 12:21:25 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: URANUS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET Planet Uranus ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=URANUS ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 5.73 +/- 0.5 Ephemeris Center: EARTH Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 17737( 6) - 04-Oct-2024 12:21:25 - [ 4] Visit: 01 Visit Requirements: BETWEEN 02-OCT-2024:02:00:00 AND 02-OCT-2024:10:00:00 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 URANUS STIS/FUV TIME-TA 25MAMAD1 G140L 1425 BUFFER-TIME=200 1 2100 S -MAMA G see below (1917 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 URANUS STIS/FUV TIME-TA 52X0.5D1 G140M 1272 BUFFER-TIME=600 1 2100 S -MAMA G see below (2134 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 URANUS STIS/FUV TIME-TA 25MAMA MIRROR BUFFER-TIME=200 1 2100 S -MAMA G see below (2037 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 URANUS STIS/FUV TIME-TA F25SRF2 MIRROR BUFFER-TIME=600 1 2100 S -MAMA G see below (2056 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 | ------------------------------------------------------------------------------------------------------------------------------------ URANUS 1 STIS/FUV TIME-TA 25MAMAD1 G140L 1425 none none none none 1 1917.0 S -MAMA G URANUS 2 STIS/FUV TIME-TA 52X0.5D1 G140M 1272 none none none none 2 2134.0 S -MAMA G URANUS 3 STIS/FUV TIME-TA 25MAMA MIRROR none none none none 3 2037.0 S -MAMA G URANUS 4 STIS/FUV TIME-TA F25SRF2 MIRROR none none none none 4 2056.0 S -MAMA G 17737( 6) - 04-Oct-2024 12:21:25 - [ 5] Visit: 02 Visit Requirements: BETWEEN 24-OCT-2024:13:30:00 AND 24-OCT-2024:14:30:00 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 URANUS STIS/FUV TIME-TA 25MAMA G140L 1425 BUFFER-TIME=200 1 2100 S POS TARG 3, -2.5 -MAMA G see below (1917 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 URANUS STIS/FUV TIME-TA 52X2 G140M 1272 BUFFER-TIME=600 1 2100 S POS TARG 0, -6 -MAMA G see below (2134 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 URANUS STIS/FUV TIME-TA 25MAMA MIRROR BUFFER-TIME=200 1 2100 S POS TARG 3, -4 -MAMA G see below (2037 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 URANUS STIS/FUV TIME-TA F25SRF2 MIRROR BUFFER-TIME=600 1 2100 S SAME POS AS 3 -MAMA G see below (2056 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 | ------------------------------------------------------------------------------------------------------------------------------------ URANUS 1 STIS/FUV TIME-TA 25MAMA G140L 1425 none none none none 1 1917.0 S -MAMA G URANUS 2 STIS/FUV TIME-TA 52X2 G140M 1272 none none none none 2 2134.0 S -MAMA G URANUS 3 STIS/FUV TIME-TA 25MAMA MIRROR none none none none 3 2037.0 S -MAMA G URANUS 4 STIS/FUV TIME-TA F25SRF2 MIRROR none none none none 4 2056.0 S -MAMA G 17737( 6) - 04-Oct-2024 12:21:25 - [ 6] Summary Form for Proposal 17737 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 25MAMA, 25MAMAD1, 52X0.5D1, 52X2, F25SRF2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=200, BUFFER-TIME=600 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 02-OCT-2024:02:00:00 AND 02-OCT-2024:10:00:00, BETWEEN 24-OCT-2024:13:30:00 AND 24-OCT-2024:14:30:00, POS TARG 0, -6, POS TARG 3, -2.5, POS TARG 3, -4, SAME POS AS 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, G140M, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names URANUS ------------------------------------------------------------------------------------------------------------------------------------