National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Mars Exploration Program Office Comet Siding Spring (C/SS) at Mars: Risk and Opportunity Presented by R. Zurek, Mars Program Office (JPL) 29 July, 2014 Comet Siding Spring HST Image: Mar 11, 2014 Mars ! ! National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Mars Exploration Mars Exploration Program Office Operational Odyssey 2016 2001 - 2014 2018 2020 2022 MRO ISRO – MOM Mangalyaan Mars Express Collaboration ESA Trace Gas Orbiter (Electra) Future Planning MAVEN Curiosity – Mars Science Laboratory Opportunity ! ! ESA ExoMars Rover (MOMA) 2020 Science Rover InSIGHT (Discovery Program) 2 2 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Mars Exploration Mars Exploration Program Office Operational Odyssey 2016 2001 - 2014 2018 2020 2022 MRO ISRO – MOM Mangalyaan Mars Express Collaboration ESA Trace Gas Orbiter (Electra) Future Planning MAVEN Curiosity – Mars Science Laboratory Opportunity ! ! ESA ExoMars Rover (MOMA) 2020 Science Rover InSIGHT (Discovery Program) 3 3 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Comet /2013 A1 Siding Spring Mars Exploration Program Office Close&up)of)Encounter) Geometry) vref = 2.0 m/s vref = 2.5 m/s normalized flux 0 0.5 1 vref = 1.5 m/s 0 1 2 3 Ame)from)c/a)[hr]) Siding Spring C/A:)Closest) Approach) • 132,000&km& Mars View from the Sun ! ! 1 2 3 0 1 time from c/a [hr] 2 • 3 current recommendation:! HST obs point to bulk grain velocities below threshold threshold for Mars impact, so the timing of the v_ref 1 Peak)flux)seGling)in)at)90&100) one most closely representing the flux of grains, if any minutes)a@er)closest)approach) • 28,000&km& Orbit)Planes)Crossing) ~95)min)a@er)C/A) 0 4 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Comet Modeling Mars Exploration Program Office Ø Model the comet-‐produced dust distribuFon as a funcFon of Fme – In fall of 2013, two modeling groups were selected through the MEP Cri@cal Data Products program to help with this: • Pasquale Tricarico, Nalin H. Samarasinha, Mark Sykes, PSI • Tony Farnham, Mike S. P. Kelley, Dennis Bodewits, U. Maryland – Also par@cipa@ng, providing @me-‐of-‐arrival of comet nucleus and debris: • Davide Farnocchia, Paul Chodas, Steven Chesley, JPL Solar System Dynamics Group – Reports have been or will soon be submiGed for publica@on • P. Tricarico et al., Astrophysical Journal LeTers, 787, L35, 2014 • Farnocchia et al., in press, Astrophysical Journal • Farnham et al., in prepara@on – Original reports and overview available on hGp://mepag.jpl.nasa.gov/cdp.cfm Ø Results of the modeling acFvity – Modeling results were constrained using available observa@ons of the comet. – Provided arrival @ming & dura@on of the comet-‐associated par@cle flux at Mars. – Characterized the comet-‐derived par@cles in terms of size and number density. ! ! 5 Modeled Par@cle Field National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Grain density 1 g/cm3, v_ref = 1 m/s Mars Exploration Program Office 1.5e+05 Fluence is es@mated to be in the 0 to 10-‐6 counts/m2 [1/km2] range • The par@cles, from 1 to 10 mm in diameter, arrive at Mars travelling 56 km/s, 80-‐110 minutes a[er closest approach of the nucleus. • Orbiters can hide behind Mars for 30-‐40 minutes, by phasing in orbit. • Rovers are protected by the Mars atmosphere, thin as it is. [km] 1e+05 • 50000 0 [km] -1e+05 ! ! -50000 0 50000 [km] 1e+05 1.5e+05 !17 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California C/SS Encounter Goals for Mars Assets Mars Exploration Program Office • Survive: Low fluence & orbit phasing take care of that • Science ObjecFves Focus on Two Areas: 1) the comet itself and 2) its potenFal impact on the Mars atmosphere. • For the comet, the goals are: Ø First-‐ever resolu@on of the nucleus of a long-‐period comet. o MRO HiRISE: 140 m/pixel on a nucleus ~ 500 to 2500 m across Ø Characterize C/SS coma & tail: Par@cle size, gas composi@on, ac@vity. o Warning: The Mars spacecra[ instruments weren’t designed for high-‐spectral resolu@on gas survey or for imaging diffuse, faint objects (as compared to Mars), but we will see what we can do. o The best instruments for comet composi@on may well be on MAVEN, which will follow orbit inser@on on Sept. 21 with maneuvers and instrument deployments as they transi@on to their nominal science orbit. • For Mars, the goals are: Ø Observe impacts of cometary gas & dust on the Mars atmosphere. ! ! o Upper Atmospheric hea@ng (>150 km) o Ionospheric enhancement o Cloud seeding? 7 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Science ObservaFons* -‐ Preliminary *Conducted only if safe, posing no spacecraft or instrument issues Mars Exploration Program Office NASA Missions Comet Mars Response v v u u u u Comet Nucleus: Size, Shape & Rota@on u Comet Ac@vity: Jets & Variable Brightness u u v v u Comet Coma: Variability, par@cle size, gas composi@on u v u u u u u Comet Tail: Par@cle Size u v v v v u u Mars Upper Atmosphere Composi@on: Neutrals, ions & electrons; meteor trails v v u u u u Mars Lower Atmosphere: Temperature and Clouds v v v v v v 1Conducted NGIMS,STATIC SWEA,SWIA LPW,MAG, SEP IUVS MastCAM CHEMCAM? PANCAM HEND/NS THEMIS VIS & IR SHARAD MARCI CTX MAVEN1 ROVERS Comet General Features Key: major contribu@on u contribu@on v ! ! ODY MCS Observa@on Objec@ve HiRISE Target CRISM MRO u only if transition to science orbit is nominal 8 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Science ObservaFons* -‐ MAVEN *Conducted only if safe, posing no spacecraft or instrument issues C/SS Nucleus Closest Approach - 2 days Possible Encounter with C/SS Debris - 1 day IUVS Comet Imaging on 5 orbits Mars Exploration Program Office + 1 day All instruments as H/V off in standard Mars MAG, LPW, SEP on science on 7 orbits + 2 days All instruments as in standard Mars science on 10 orbits: • Charged par@cles, Ne & Te, Ions/neutrals • MAG, IUVS limb & coronal scans: Mars imaging (lyA, OH, D/H) MAVEN Example • Science opera@ons begin 2 days early to observe Mars, interrupted for safety during peak dust @me, resume for 2 days post encounter, then resume nominal transi@on plan. • Pre-‐encounter imaging to determine ac@vity level, composi@on, gas/dust, etc. Also view Mars as baseline for post-‐encounter effects. • Spacecra[ in safe configura@on during close encounter and dust tail passage, implies safest aqtude and instrument High Voltage (H/V) off. • Periapsis of 4.5 hr orbit is behind Mars at predicted @me of peak dust flux. ! ! 9 National Aeronautics and Space Administration Science ObservaFons* -‐ MRO Jet Propulsion Laboratory California Institute of Technology Pasadena, California *Conducted only if safe, posing no spacecraft or instrument issues C/SS Nucleus Closest Approach - 2 days Mars Exploration Program Office Possible Encounter with C/SS Debris + 1 day - 1 day Periodic C/SS Observa@ons each 2hr orbit + 2 days Periodic C/SS Observa@ons on each 2hr orbit C/A C/A – 1 orbit: 2 CRISM + 13 HiRISE scans Various line @mes to provide different exposures; CTX R/A C/A orbit: 2 CRISM + 10 HiRISE scans + CTX R/A Shortest line @mes for best resolu@on; MCS obs of coma (TBD) Key: C/A = Closest Approach; R/A = Ride-‐Along ! ! Center @me for C/SS par@cle encounter with Mars: 20:07 ± 10 min UT 20:46:49 19:43:51 C/SS C/A 18:31 UT 19:01:52 18:12:16 17:39:30 16:38:26 MRO Example C/A + 1 orbit: 2 CRISM + 13 HiRISE scans Various line @mes to provide different exposures, CTX R/A Nadir observa@ons C/SS observa@ons 10 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Science ObservaFons* -‐ Mars ODY Mars Exploration Program Office • ObjecFve: – Emphasis on the unique contribu@ons to be made by THEMIS: moderate resolu@on infrared spectral imaging. • THEMIS: 3 proposed, prioriFzed observaFons: – Obtain highest possible spa@al resolu@on images over as much of the coma as possible during one observing period (±26 hr?). • Image coma as close to closest approach to Mars as possible. – Obtain complete coverage of the coma and tail at moderate spa@al resolu@on. – Obtain an image of the enVre coma and tail above the Mars limb to provide context of the coma rela@ve to the known temperature and gas and dust opacity of the Mars atmosphere. • ! ! 11 Neutron Spectrometer and HEND: – Nominal observa@ons while in nadir-‐point aqtude to monitor effects on neutral and charged par@cle fluxes. National Aeronautics and Space Administration Science ObservaFons* -‐ Opportunity & Curiosity Jet Propulsion Laboratory California Institute of Technology Pasadena, California Mars Exploration Program Office ! ! 12 • When the comet is at closest approach, the local @mes at Opportunity and Curiosity will be early morning and late a[ernoon, respec@vely, so the comet would be viewed thru the dayside sky. – It is also mid-‐southern spring, a @me when extensive dust storms may occur, further reducing visibility. • Best viewing will be pre-‐dawn and post-‐dusk on the encounter sol, but several hours before and a[er closest approach. National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Next Steps Mars Exploration Program Office • Phasing Maneuvers Ø Ø Ø Ø • • July 2 August 5 August 27 October 9 MRO 1st of 2 phasing maneuvers (OTM 37) ODY phasing maneuver, if required MRO 2nd of 2 phasing maneuvers (OTM 38) MAVEN will combine with 3rd period reduction maneuver (PRM-3) during transition to science orbit Get Comet Encounter Observation Sequences finalized Interactions with Comet Science Community Ø Ongoing: Participation in Coordinated Investigations of Comets (CIOC) forum Ø August 11: Workshop involving Mars Projects and other Comet Observers o Give status on Mars spacecraft comet observing plans; seek comment from community. o Review latest observations and observation plans. Ø September 19: Virtual Meeting between Mars Projects and Comet Scientists o Give status on final science observing plans by Mars Projects. o Review latest observations. ! ! • September 19: Provide update on mitigation status and observation planning • October 19: Closest Approach of Comet Siding Spring to Mars Ø Prime observing campaign ±2.5 days around nucleus closest approach 13
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