Constraining the Surface Composition of Europa with Spatially Resolved Mid-UV Spectra

0 Assigned ID: 766 ----- Attempting Submission 1 (Fri Apr 07 19:11:53 GMT 2017) ----- I've updated the orbit planner. Thank you! 1027572425 ----- Attempting Submission 1 (Wed Jul 19 16:09:46 GMT 2017) ----- ----- Attempting Submission 2 (Fri Oct 06 15:30:32 GMT 2017) ----- ----- Attempting Submission 3 (Mon Oct 09 15:50:24 GMT 2017) ----- ----- Attempting Submission 4 (Mon Mar 05 15:39:55 GMT 2018) ----- ----- Attempting Submission 5 (Tue Mar 13 15:13:32 GMT 2018) ----- ----- Attempting Submission 6 (Tue Jun 26 20:17:31 GMT 2018) ----- ----- Attempting Submission 7 (Sat Dec 15 16:28:22 GMT 2018) ----- Constraining the Surface Composition of Europa with Spatially Resolved Mid-UV Spectra We propose to observe Jupiter's icy moon, Europa, to obtain spatially resolved UV spectra of its leading, trailing, sub-Jovian and anti-Jovian hemispheres that include diagnostic mid-UV wavelengths that have not previously been analyzed. Current published observations of Europa include near-UV observations from 210 nm - 320 nm, and far-UV observations from ~110 nm - 170 nm; however, the data in the mid-UV (170 nm - 210 nm) is lacking. Although Europa's surface consists mostly of water ice, the characteristic sharp absorption edge observed at ~165 nm in lab spectra and on the icy moons of Saturn has not been detected on Europa. Observations in the mid-UV could reveal the absorption edge at longer wavelengths, suggestive of larger ice grains on the surface. Conversely, the mid-UV spectrum could verify that the water ice absorption edge is not present on Europa. The reflectance of Europa's hemispheres drops significantly between the near- and far-UV. The spectral shape in the mid-UV will be used to constrain the surface composition across the satellite. Mid-UV observations with STIS will span the previous near- and far-UV data sets, providing a seamless UV spectrum. These observations will provide the first spatially resolved spectra of each of Europa's hemispheres in the mid-UV. We will use the STIS G230L mode with the 52 x 0.2 slit centered at 237.6 nm. We will use a pattern to shift the slit one time on Europa to cover the central ~0.4 arcseconds of the ~1" sized satellite and still obtain useful SNR at the shortest wavelengths. The observations will be scheduled such that we observe the sub-Jovian, leading, anti-Jovian, and trailing hemispheres (0 deg, 90 deg, 180 deg, and 270 deg orbital longitudes). Depening on the exact timing of the visits, the observations will need to be offset slightly from 0 or 180 deg to avoid observing Europa while in transit of Jupiter, or in eclipse by Jupiter, respectively. We request to observe Europa when the Jovian system is within 5 weeks of opposition, which occurs on May 9, 2018, to maximize Europa's size, increase its brightness (and SNR), and reduce background from terrestrial UV airglow from ~10-15 kilorad (kR) to ~2.4 - 4 kR. We assume a 5 minute acquisition time for the target, followed by a 2400 s observation period, consisting of two exposures for each visit. The first exposure will be offset from the center of Europa by -0.1" and the second will be offset by +0.1" perpendicular to the slit, such that the 0.2" wide slit covers 0.4" of the central part of Europa's surface. The spectral range covered by this instrument (157 - 318 nm) will provide a spectrum covering the mid-UV wavelengths not previously studied. This spectral range will confirm the lack of a water-ice absorption edge in the UV spectra on all hemispheres of Europa and will be used to constrain the composition of Europa's surface. Solar System 6 false false false false false false false SUPPORTED SOLAR SYSTEM YES SATELLITE Europa at Eastern Elongation STD=JUPITER STD=EUROPA OLG OF EUROPA-EAST FROM EARTH BETWEEN 75 105, SEP OF EUROPA-EAST CALLISTO FROM EARTH GT 10", SEP OF EUROPA-EAST IO FROM EARTH GT 10", SEP OF EUROPA-EAST GANYMEDE FROM EARTH GT 10" EARTH SOLAR SYSTEM YES SATELLITE Europa at Western Elongation STD=JUPITER STD=EUROPA SEP OF EUROPA-WEST CALLISTO FROM EARTH GT 10", SEP OF EUROPA-WEST IO FROM EARTH GT 10", SEP OF EUROPA-WEST GANYMEDE FROM EARTH GT 10", OLG OF EUROPA-WEST FROM EARTH BETWEEN 255 285 EARTH SOLAR SYSTEM YES SATELLITE Europa at near 0 deg orb longitude STD=JUPITER STD=EUROPA SEP OF EUROPA-SUBJUP CALLISTO FROM EARTH GT 10", SEP OF EUROPA-SUBJUP IO FROM EARTH GT 10", SEP OF EUROPA-SUBJUP GANYMEDE FROM EARTH GT 10", OLG OF EUROPA-SUBJUP FROM EARTH BETWEEN 340 20 EARTH SOLAR SYSTEM YES SATELLITE Europa near 180 deg orbital longitude STD=JUPITER STD=EUROPA SEP OF EUROPA-ANTIJUP CALLISTO FROM EARTH GT 10", SEP OF EUROPA-ANTIJUP IO FROM EARTH GT 10", SEP OF EUROPA-ANTIJUP GANYMEDE FROM EARTH GT 10", OLG OF EUROPA-ANTIJUP FROM EARTH BETWEEN 160 200 EARTH STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/NUV-MAMA Spectroscopic No No G230L 2376 POS-TARG MOSAIC DITHER 0.2 If the center of Europa is (x,y) = (0,0) and 'x' is perpendicular to the slit, then the first point in the pattern should be (-0.1", 0"), the second point should be (+0.1", 0"). STIS-ALONG-SLIT false true 2 0.0 POS-TARG STIS-PERP-TO-SLIT 90.0 2

false

1549483704779 The scheduling data was generated by CASM 26.2.2. CASM was run in Phase II mode. /private/var/folders/z3/xy_g1v_s5fz9yrhzb8thz4cr0001qc/T/OPVisit13721619969022697587.xml The leading hemisphere of Europa can be observed when Europa is at an orbital longitude of 90 degrees. This is when Europa is at eastern elongation. 1528237876000 88.98479998931231 (Tic-Visit :proposal-id 15095 :visit-id "01" :proposal-version -1 :trans-version "20181130" :date "06-Feb-2019 15:08:24.0" :trans-errors '(:WARNINGS 1 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 1409584 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15095 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15095 :visit-id "01" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2868 :al-overhead-at-end 0 :internal-dur-at-end 440 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3142 :pcs-gap 0 ) true 1 1 1549483706345 Using ephemeris for target 15095-51-EUROPA-EAST ephemeris data for target 15095-51-EUROPA-EAST does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 18.070 to 20.032. ephemeris interval: 19.031 to 21.032 The scheduling data was generated by CASM 27.0. CASM was run in Phase II mode. /private/var/folders/z3/xy_g1v_s5fz9yrhzb8thz4cr0001qc/T/OPVisit12588554163608309686.xml The leading hemisphere of Europa can be observed when Europa is at an orbital longitude of 90 degrees. This is when Europa is at eastern elongation. (Tic-Visit :proposal-id 15095 :visit-id "51" :proposal-version -1 :trans-version "20181130" :date "06-Feb-2019 15:08:25.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 1409584 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15095 :visit-id "51" :obset-id "51" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15095 :visit-id "51" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2748 :al-overhead-at-end 0 :internal-dur-at-end 440 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3142 :pcs-gap 0 ) true 1 0 1549483707730 Using ephemeris for target 15095-02-EUROPA-WEST ephemeris data for target 15095-02-EUROPA-WEST does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 18.070 to 19.335. ephemeris interval: 18.334 to 20.336 The scheduling data was generated by CASM 26.2.2. CASM was run in Phase II mode. /private/var/folders/z3/xy_g1v_s5fz9yrhzb8thz4cr0001qc/T/OPVisit17218585019117147760.xml The trailing hemisphere of Europa can be observed when Europa is at an orbital longitude of 270 degrees. This is when Europa is at western elongation. 1524104640000 253.74670316872175 (Tic-Visit :proposal-id 15095 :visit-id "02" :proposal-version -1 :trans-version "20181130" :date "06-Feb-2019 15:08:27.0" :trans-errors '(:WARNINGS 1 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 1409584 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15095 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15095 :visit-id "02" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2868 :al-overhead-at-end 0 :internal-dur-at-end 440 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3142 :pcs-gap 0 ) true 1 1 1549483709013 Using ephemeris for target 15095-03-EUROPA-SUBJUP ephemeris data for target 15095-03-EUROPA-SUBJUP does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 18.070 to 19.335. ephemeris interval: 18.334 to 20.336 The scheduling data was generated by CASM 26.2.2. CASM was run in Phase II mode. /private/var/folders/z3/xy_g1v_s5fz9yrhzb8thz4cr0001qc/T/OPVisit14674828147627267289.xml The sub_Jovian hemisphere of Europa can be observed when Europa is at an orbital longitude near 0 degrees. This is when Europa is near eclipse. We do not want Europa to be in eclipse for the observation, however 1527846285000 129.75 (Tic-Visit :proposal-id 15095 :visit-id "03" :proposal-version -1 :trans-version "20181130" :date "06-Feb-2019 15:08:28.0" :trans-errors '(:WARNINGS 1 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 1409584 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15095 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15095 :visit-id "03" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2868 :al-overhead-at-end 0 :internal-dur-at-end 440 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3142 :pcs-gap 0 ) true 1 1 1549483710288 Using ephemeris for target 15095-04-EUROPA-ANTIJUP ephemeris data for target 15095-04-EUROPA-ANTIJUP does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 18.070 to 19.335. ephemeris interval: 18.334 to 20.336 The scheduling data was generated by CASM 26.2.2. CASM was run in Phase II mode. /private/var/folders/z3/xy_g1v_s5fz9yrhzb8thz4cr0001qc/T/OPVisit16515895368798332366.xml The anti-Jovian hemisphere of Europa can be observed when Europa is at an orbital longitude of 180 degrees. We will observe Europa near this longitude, but do not want it to be transiting Jupiter during the observation. 1523429464000 303.44337545844 (Tic-Visit :proposal-id 15095 :visit-id "04" :proposal-version -1 :trans-version "20181130" :date "06-Feb-2019 15:08:29.0" :trans-errors '(:WARNINGS 1 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 1409584 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15095 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15095 :visit-id "04" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2868 :al-overhead-at-end 0 :internal-dur-at-end 440 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3142 :pcs-gap 0 ) true 1 1