0 Assigned ID: 5533 ----- Attempting Submission 1 (Tue Mar 26 18:06:16 GMT 2024) ----- Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Sensitive exposures should have an ETC run number provided. Scheduled Visit 02 for sometime in fall 2026. Please generate target confirmation charts for this before finalizing. 531561587 ----- Attempting Submission 1 (Thu Aug 08 23:07:48 GMT 2024) ----- ----- Attempting Submission 2 (Tue Oct 15 21:31:21 GMT 2024) ----- ----- Attempting Submission 4 (Mon Nov 18 19:25:17 GMT 2024) ----- ----- Attempting Submission 5 (Tue Mar 18 18:49:10 GMT 2025) ----- ETC run numbers are not required as I have followed the same guidelines as the previous numerous observations of Mars. Determining the total amount of water lost by Mars over its ~4.3 billion year history has been the subject of contention in the Mars community for the past few decades. Recent advances led to the discovery of a magnitude change in water escape rate during the perihelion season every Mars year. This has increased the initial estimates of the total amount of water lost by Mars from 3.6m of Global Equivalent Layer (GEL) to 23m, an increase by a factor of 5. Another recent discovery with HST has been detecting the observational signature of non-thermal/hot H in the exosphere of Mars. The escape rate of such atoms was found to be ~26% of the thermal escape rate at solar minimum, further elevating the water loss estimates from Mars. Data analysis revealed that solar wind is the major driver in the creation of this population. At present the effect of solar activity on the creation of hot H at Mars and the consequence on water escape rate is unknown. Hence the proposal is to determine the correlation between non-thermal H escape rate and solar activity at Mars. Characterizing this population is critical as hot H atoms are present in the exospheres of all solar system planets and likely exoplanets as well. Because the younger Sun was more active, and there are many exoplanetary systems with active star hosts, escape of hot H could have important implications on the habitability and water escape history of planets. This proposal supports the HST UV initiative. We propose to obtain ACS SBC UV images of Mars to study the characteristics of the non-thermal hydrogen atoms populating the exosphere of Mars. Hydrogen atoms resonantly scatter solar Lyman alpha photons (far-ultraviolet wavelengths) that can be imaged using the ACS detector and a combination if filters onboard the HST. More specifically, each observing run would be a series of clear and filtered images, with the F140LP filter used to image Mars with the Lyman alpha photons blocked and the F115LP (clear) filter which allows the Lyman alpha emission from Mars through to the detector. The scaled difference between the clear and filtered images reveals the Lyman alpha coming from the hydrogen atoms present in the exosphere of Mars. This is very effective in studying the Martian exosphere, as above ~250 km from the Martian surface most of the emission is Lyman alpha. Sky observations near Mars are critically important to accurately subtract the Lyman alpha emissions coming from the background geocorona and interplanetary hydrogen. The allotted orbits would be divided into a series of 3 visits of 2 orbits each, one observing Mars and one for the sky background 5 arcminute away from Mars for a total of 5 orbits. The three visits would be spaced over a time period of 2.5 months which would allow us to monitor changes in the hot hydrogen population at Mars as Mars approaches aphelion and crosses it at solar maximum. HST is the only facility that has the UV sensitivity, necessary angular resolution as well as much larger altitude coverage in order to image the extended hot hydrogen exosphere of Mars. While MAVEN and MEX are capable of measuring the lower exosphere with higher altitude resolution that is fruitful towards studying latitudinal differences, they are not capable of imaging the more energetic hydrogen atoms that reside at the highest reaches of the Martian exosphere. This study will greatly aid in providing a better estimate of the timeline for the water loss history from Mars. The ACS/SBC clear (F115LP) images will be taken during the shadow portion of HST's orbit, and the filtered (F140LP) images will be taken when HST is in sunlight to minimize the brightness contributed by the geocoronal H atoms at Lyman alpha. One HST orbit during each observing run will be dedicated towards measuring the background emissions from the interplanetary hydrogen and the geocorona. It is imperative that the background emissions be measured relative to HST's orbital location as experience with past programs has shown that the geocorona is too variable to be modeled with high accuracy for deriving the Lyman alpha emissions from the Martian exosphere. This is very important towards determining the faint emissions from the Martian hydrogen exosphere far from Mars. The count rates for ACS SBC clear (F115LP) imaging of Mars range from 5000-80000 counts/sec as determined from earlier HST observing campaigns. This count rate is well below the limit of 200,000 counts/sec, and the local count rate limits are also not exceeded. Count rates with F140LP filter are much lower since this filter blocks Lyman alpha emission. The roll angle will be unconstrained for this program. Since Mars moves accross the sky, this generally makes it possible to locate good guide stars within any week-long observing window, and it has been shown in GO 11170, 13794, and 14752 that bright object protection and counting rate limits will not hinder the observations, even when Mars is close to the Sun. PI Dolon Bhattacharyya has been studying water escape from Mars with HST ACS-SBC and STIS for the past decade and has 5 first author publications on the same. The PI also has several co-author publications with MAVEN-IUVS data looking at the D an H Lyman-alpha emission from the Martian exosphere. Dr. Bhattacharyya is an expert at modeling H Lyman-alpha emissions from planetary exospheres. Dr. Bhattacharyya is also familiar with the ACS-SBC detector having led the HST calibration program to determine its sensitivity at Lyman-alpha. Dr. Bhattacharyya will lead the study with the planning and execution of Phase 2 as well as analysis and modeling of the Mars Lyman alpha observations. Co-I John Clarke is an expert in all aspects of HST and was the Project scientist and instrument scientist from 1984-1987. Prof. Clarke has been studying the exosphere of Mars for more than a decade with the HST ACS-SBC imager and was the first to implement the technique of subtracting the F40LP image from the F115LP image to obtain the Martian Lyman-alpha signal with high S/N. Prof. Clarke will advise on the observation planning process and contribute towards the analysis of the data and interpretation of the results. Co-Is Valery Shematovich and Dmitry Bisikalo are experts in the Monte Carlo modeling of non-thermal H in the exosphere of Mars. They have multiple peer-reviewed (6) publications in prestigious journals on the topic. Their model will be used to determine the number density and energy distribution of the non-thermal H population in the exosphere of Mars. Solar System Astronomy Solar System Astronomy 6 false true false false false false false SUPPORTED SOLAR SYSTEM PLANET Mars exospheric Ly-a emission STD=MARS TYPE=POS_ANGLE,RAD=12,ANG=172,REF=NORTH NOT OCC OF MARS-EXOSPHERE BY MARS FROM EARTH EARTH SOLAR SYSTEM PLANET Sky background near Mars STD=MARS TYPE=POS_ANGLE,RAD=300,ANG=0,REF=NORTH NOT OCC OF SKY-NEAR-MARS BY MARS FROM EARTH EARTH SOLAR SYSTEM PLANET Extended exosphere of Mars with non-thermal H dominating portions STD=MARS TYPE=POS_ANGLE,RAD=35,ANG=172,REF=NORTH NOT OCC OF MARS-EXOSPHERE-EXTENDED BY MARS FROM EARTH EARTH ACS/SBC Imaging No No F115LP ACS/SBC Imaging No No F140LP ACS/SBC Imaging No No F115LP ACS/SBC Imaging No No F140LP 1731957803162 Using ephemeris for target 17762-01-MARS-EXOSPHERE ephemeris data for target 17762-01-MARS-EXOSPHERE does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 24.300 to 26.120. ephemeris interval: 25.059 to 27.060 Using ephemeris for target 17762-01-MARS-EXOSPHERE-EXTENDED ephemeris data for target 17762-01-MARS-EXOSPHERE-EXTENDED does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 24.300 to 26.120. ephemeris interval: 25.059 to 27.060 Using ephemeris for target 17762-01-SKY-NEAR-MARS ephemeris data for target 17762-01-SKY-NEAR-MARS does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 24.300 to 26.120. ephemeris interval: 25.059 to 27.060 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. 1732656944000 279.4018338498818 (Tic-Visit :proposal-id 17762 :visit-id "01" :proposal-version -1 :trans-version "20240604" :date "18-Nov-2024 11:23:22.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "28" :si-bright-earth-limb-angle 20.0 :data-volume 833296 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17762 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Obset :proposal-id 17762 :visit-id "01" :obset-id "A1" :pcs-mode "FGS" ) (Tic-Obset :proposal-id 17762 :visit-id "01" :obset-id "B1" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17762 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2102 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2645 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17762 :visit-id "01" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2102 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2645 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17762 :visit-id "01" :orbit-number 3 :pcs-time 380 :si-vis-utilization 2102 :al-overhead-at-end 0 :internal-dur-at-end 340 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2645 :pcs-gap 0 ) true 3 0 1773337321464 The scheduling data was generated by CASM 34.0. CASM was run in Phase II mode. /System/Volumes/Data/solaris/user1/bporterfield/hst/work/OP-cache/17762-v02.xml (Tic-Visit :proposal-id 17762 :visit-id "02" :proposal-version -1 :trans-version "20250929" :date "12-Mar-2026 13:42:01.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "28" :si-bright-earth-limb-angle 20.0 :data-volume 833296 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17762 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Obset :proposal-id 17762 :visit-id "02" :obset-id "A2" :pcs-mode "FGS" ) (Tic-Obset :proposal-id 17762 :visit-id "02" :obset-id "B2" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17762 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2102 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2979 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17762 :visit-id "02" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2102 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2979 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17762 :visit-id "02" :orbit-number 3 :pcs-time 380 :si-vis-utilization 2102 :al-overhead-at-end 0 :internal-dur-at-end 340 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2979 :pcs-gap 0 ) true 3 0