Target CERES-OCCATOR: There is no need or capability to test the scheduling of observations of moving targets in Phase I. This warning will go away the next time the proposal is loaded. 0 Assigned ID: 3672 ----- Attempting Submission 1 (Fri Mar 25 22:59:11 GMT 2022) ----- HST Phase I Proposal 3672 successfully submitted. Receipt: # 3672-1 ----- Attempting Submission 2 (Fri Mar 25 23:01:03 GMT 2022) ----- The warning is because Ceres is a moving target, which does not enable planning with the visit planner in phase I. STIS SCIENCE TOO FAR FROM WAVECAL STIS SCIENCE TOO FAR FROM WAVECAL STIS SCIENCE TOO FAR FROM WAVECAL STIS SCIENCE TOO FAR FROM WAVECAL STIS SCIENCE TOO FAR FROM WAVECAL STIS SCIENCE TOO FAR FROM WAVECAL MISSING FRINGE FLAT CALIBRATION ORBITAL VISIBILITY OVERRUN Comments below are from a previous submission: Loosened the CML constraints and slightly shortened exposure times to get rid of the orbital visibility overrun caused by the "Home" after acquisition. The only overrun now is the wavecal, which should be able to be pushed into occultation. I am not sure why the APT still says overrun for that. The above changes resulted in more visibility windows. I deleted the peak-up and currently do the acquisition on Ceres, before doing a slit-step pattern on the Level-2 Ceres-Occator target. My understanding was that this would have the telescope use its acquisition on the body itself and then make the small pointing offset to the actual science target based on the Level 2 coordinates in my Ceres-Occator target definition. However, it appears from the orbit planner that it may actually be throwing out the acquisition and starting from scratch on moving to the actual science target, as there is a long “home” period visible in the orbit (which also is eating up a fair bit of time that would otherwise allow for longer exposures and no target visibility overrun). Is there a way to specify this differently and ensure that the telescope is using the previous acquisition information and then applying the small offset to the crater from the planetocentric coordinates I provided? I manually input a longer fringe flat following the example you sent, as well as some exposure time guidelines I found online. I think what I have done should give double the SNR as the default settings, but I would appreciate a check on this. Comments below are from a previous submission: Resubmitting because was ablee to get orbital visibility overrun warnings to go away. CS Amy Jones noted that switching the order of the G750L wavecal and fringe flat fixed the warning, for an unknown reason. However, for me, switching that order and then switching it back, got the warnings to go away. So, the wavecal is still before the fringe flat and in occultation, but now I do not see a warning, even though there was no change in terms of what was actually overrunning the visibility and in what order. Since, it is no longer giving me issues with the wavecal in occultation, I have extended the exposure times in G430L slightly to fill the visibility. Comments below are from previous submission: The orbital visibility overrun warnings seem to only be due to the G750L wavecal being pushed into occultation. We do not think that any of the science exposures are overrun. However, we were unable to get the warnings to go away. Ideally, we would push one of the wavecals into occultation to maximize science exposure time. Regarding acquisition, we are not sure if peak-up will work on the science target (Occator crater), as the bright spots within the crater at at sub-pixel resolution. So, the pixel centered on Occator may only be a fraction brighter than surrounding pixels. If peak-up on the acquisition target (Ceres) before moving to the science target for science exposures would improve the accuracy of the offset by increasing the accuracy of the initial target centering, then perhaps that is an alternative if peak-up on the science target is not feasible. We had significant confusion regarding defining the science target and its observing windows. We specify the location of the crater using level 2 planetocentric coordinates, which we understand to be defined as positive east. Not only do we need the crater to be visible (not occulted by Ceres itself), but we also need it to be near the center of the disk during the science exposures. For this reason, we also specify a CML constraint. From the online documentation on CML, we see that for dwarf planets, the CML is defined using a right-handed coordinate system, which we would have interpreted as also positive east, rather than planetographic coordinates, which are positive west. However, specifying a CML near the planetocentric longitude of Occator did not work (as it should have if both were defined in the same sense), as the APT seemed to treat those two constraints (Occator not occulted and the CML) as mutually exclusive and incompatible with each other. If we instead define the CML as positive west (so 360 - planetocentric), then the APT sees the two conditions as compatible and finds schedulable windows, so this is what we have done. However, this seems in direct contradiction to the online documentation for how CML is defined for dwarf planets (as opposed to planets and satellites), unless our interpretatino of the online documentation is incorrect. We would really appreciate a check on this point of confusion, as precise pointing to the science target is crucial for our science. Thank you! -2063736962 ----- Attempting Submission 1 (Wed Jul 13 00:01:37 GMT 2022) ----- ----- Attempting Submission 2 (Thu Jul 14 16:48:08 GMT 2022) ----- ----- Attempting Submission 3 (Tue Mar 28 22:43:29 GMT 2023) ----- ----- Attempting Submission 4 (Tue Apr 04 19:57:04 GMT 2023) ----- Manual fringe flat to get higher S/N. Only orbital visibility overrun is due to the wavecal, which should be able to occur during occultation. We propose targeted single-orbit STIS observations of Ceres' Occator crater in order to unambiguously confirm or reject the possible identification of sodium chloride color centers in Dawn visible-channel spectra of Occator's bright spots Cerealia and Vinalia Faculae. The Dawn visible channel was affected by perplexing artifacts resulting in anomalous spectral shapes that required improvised, empirical calibration steps, and the published visible-channel spectra of Cerealia Facula across different image cubes and reasonable reduction methods appear to disagree. Though some exhibit features potentially consistent with sodium chloride, others show a complete lack of visible spectral features altogether. As abundant sodium chloride is expected for faculae formation mechanisms involving a relict ocean brine reservoir, resolving this ambiguity would be an important step toward understanding not just the formation and evolution of Ceres' enigmatic bright spots, but also its potential status as a relict ocean world. We propose to obtain spectra in the G430L and G750L first-order spectroscopy modes using a single 0.05" slit position centered on Occator crater. We take the most conservative approach in estimating our required signal-to-noise ratio (SNR) and corresponding exposure times, based on the weaker M-center feature potentially seen in Dawn spectra. Despite the objective weakness of this potential feature, a 5-sigma detection is possible with an SNR of 185 per pixel, given the 0.09 micron FWHM of the feature and the 4.92 Angstrom/pixel dispersion in G750L. We then estimate the necessary exposure time in two ways. First, we scale from the SNR of 73 achieved by 6-second archival G750L exposures of Io with the 0.1" slit. Accounting for the slit change and the difference in brightness between Io and the expected brightness of an Occator pixel (given the relative sizes and albedos of the faculae and background), we estimate an exposure time of 180 seconds to achieve an SNR of 185 at 0.72 microns. Second, we independently estimate the time needed for our calculated SNR using the STIS exposure time calculator (using a 0.83" extended source and solar spectral shape normalized to the appropriate V-magnitude), which gives an exposure time of 209 seconds (with a time to saturation of 337 seconds) in very good agreement. As the possible F-center signatures on Ceres are at least 4.5 times as strong as their M-center counterparts, the same exposure time in G430L will provide an even stronger F-center detection, despite the slightly lower SNR (156 per pixel for a 180-second exposure) in this setting. A single orbit will allow for multiple such exposures, and therefore a higher SNR and even better detection/rejection limits. We propose to place the 0.05" slit across Occator crater for the duration of one orbit to obtain the highest possible SNR spectra in G430L and G750L. Though the features we aim to constrain may appear quite weak by our conservative estimates, the combination of such high SNR and the knowledge of exactly in which pixel the features should be strongest will allow for strong constraints via the calculations laid out above and careful comparison to pixels away from the crater. Indeed, we anticipate that considered estimation of the background Ceres signal and ratios to off-crater pixels will allow for more robust detections and removal of any unanticipated systematics. In the event of reduced-gyro operations, the main impacts to this program are expected to be reduced schedulability, as these observations are already time-constrained, and increased overheads for target acquisition, resulting in reduced science exposure times. The PI has extensive experience with STIS spectroscopy of solar system targets in both of the first-order spectroscopy modes proposed, including the mapping of weak <1 - 3% O2 absorption features on Ganymede using G750L data. Solar System Astronomy 6 false false false false false false false false AVAILABLE SOLAR SYSTEM This is the science target, Occator crater on Ceres. FEATURE FEATURE CERES STD=CERES TYPE=PCENTRIC,LONG=239.33,LAT=19.82,RAD=477.4 NOT OCC OF CERES-OCCATOR BY CERES FROM EARTH, CML OF CERES FROM EARTH BETWEEN 96 146 EARTH SOLAR SYSTEM YES This is the acquisition target, Ceres. DWARF-PLANET DWARF-PLANET CERES STD=CERES EARTH STIS/CCD Spectroscopic No No G430L 4300 STIS/CCD Spectroscopic No No G750L 7751 POS-TARG MOSAIC DITHER 0.05 STIS-ALONG-SLIT false true 3 0.0 POS-TARG STIS-PERP-TO-SLIT 90.0 1 false 1680637560270 /private/var/folders/5l/q1nxxvqd13d2150cg8wy0lbc0000gq/T/OPVisit5313938324988058058.xml Using ephemeris for target 17150-01-CERES-ACQ ephemeris data for target 17150-01-CERES-ACQ does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 22.213 to 24.182. ephemeris interval: 23.090 to 25.091 Using ephemeris for target 17150-01-CERES-OCCATOR ephemeris data for target 17150-01-CERES-OCCATOR does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 22.213 to 24.182. ephemeris interval: 23.090 to 25.091 The scheduling data was generated by CASM 31.0. CASM was run in Phase II mode. Timing windows are selected such that Ceres is near its maximum diameter of ~0.8" on the sky. (Tic-Visit :proposal-id 17150 :visit-id "01" :proposal-version -1 :trans-version "20220630" :date "04-Apr-2023 15:45:45.0" :trans-errors '(:WARNINGS 8 :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 128064 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17150 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Obset :proposal-id 17150 :visit-id "01" :obset-id "A1" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17150 :visit-id "01" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2765 :al-overhead-at-end 0 :internal-dur-at-end 1148 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3142 :pcs-gap 0 ) true 1 1 More iterations and longer exposure times for increased S/N.