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 Mars Exploration California Institute of Technology Pasadena, California Mars Exploration Program Office
Operational 2001 - 2014 2016 2018 2020 2022
Odyssey MRO
ISRO – MOM Mars Express Mangalyaan ESA Trace Gas Collaboration Orbiter (Electra)
Future Planning MAVEN
Curiosity – Mars Science 2020 Laboratory ESA ExoMars Rover (MOMA) Science Rover Opportunity InSIGHT (Discovery Program)
2 2 National Aeronautics and Space Administration Jet Propulsion Laboratory Mars Exploration California Institute of Technology Pasadena, California Mars Exploration Program Office
Operational 2001 - 2014 2016 2018 2020 2022
Odyssey MRO
ISRO – MOM Mars Express Mangalyaan ESA Trace Gas Collaboration Orbiter (Electra)
Future Planning MAVEN
Curiosity – Mars Science 2020 Laboratory ESA ExoMars Rover (MOMA) Science Rover Opportunity InSIGHT (Discovery Program)
3 3 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Comet /2013 A1 Siding Spring Pasadena, California Mars Exploration Program Office
Close&up)of)Encounter) Geometry)
vref = 1.5 m/s vref = 2.0 m/s vref = 2.5 m/s vref = 3.0 m/s 1 0.5 normalized flux 0 0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3 Siding Spring Ame)from)c/a)[ hr ]) time from c/a [hr] C/A:)Closest) Approach) 132,000&km& • current recommendation:!
Mars 28,000&km& • HST obs point to bulk grain velocities below threshold or just at Orbit)Planes)Crossing) threshold for Mars impact, so the timing of the v_ref 1.5 m/s is the ~95)min)a@er)C/A) • Peak)flux)seGling)in)at)90&100) View from the Sun one most closely representing the flux of grains, if any; minutes)a@er)closest)approach) 4 • peak flux 90-100 min. after c/a, central time: 2014 Oct 19 at 20:04 UT!
• flux from higher v_ref possible but needs to be scaled to few- percent level, small effect on overall fluence and timing
!5 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Comet Modeling Pasadena, California Mars Exploration Program Office Ø Model the comet-produced dust distribu on as a func on of me – 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 submi ed for publica on • P. Tricarico et al., Astrophysical Journal Le ers, 787, L35, 2014 • Farnocchia et al., in press, Astrophysical Journal • Farnham et al., in prepara on – Original reports and overview available on h p://mepag.jpl.nasa.gov/cdp.cfm Ø Results of the modeling ac vity – 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 National Aeronautics and Space Administration Jet Propulsion Laboratory Modeled Par cle Field 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 1e+05 • 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. [km] 50000 • Orbiters can hide behind Mars for 30-40 minutes, by phasing in orbit.
• Rovers are protected by the Mars 0 atmosphere, thin as it is.
[km] -1e+05 -50000 0 50000 1e+05 1.5e+05 [km] !17
National Aeronautics and Space Administration Jet Propulsion Laboratory C/SS Encounter Goals for Mars Assets California Institute of Technology Pasadena, California Mars Exploration Program Office • Survive: Low fluence & orbit phasing take care of that • Science Objec ves Focus on Two Areas: 1) the comet itself and 2) its poten al 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 Science Observa ons* - Preliminary Pasadena, California *Conducted only if safe, posing no spacecraft or instrument issues Mars Exploration Program Office NASA Missions MRO ODY ROVERS MAVEN1
Target Observa on Objec ve SEP CTX MCS IUVS HiRISE CRISM MARCI THEMIS VIS & IR SHARAD PANCAM HEND/NS MastCAM LPW,MAG, SWEA,SWIA CHEMCAM? NGIMS,STATIC
Comet General Features 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
Comet Coma: Variability, par cle size, gas u v u u u u u composi on
Comet Tail: Par cle Size u v v v v u u
Mars Upper Atmosphere Composi on: v v u u u u u Neutrals, ions & electrons; meteor trails
Mars Response Mars Lower Atmosphere: Temperature v v v v v v and Clouds
Key: major contribu on u contribu on v 1Conducted only if transition to science orbit is nominal
8 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Science Observa ons* - MAVEN Pasadena, California *Conducted only if safe, posing no spacecraft or instrument issues Mars Exploration Program Office
C/SS Nucleus Closest Approach Possible Encounter with C/SS Debris - 2 days - 1 day + 1 day + 2 days
IUVS Comet All instruments as H/V off All instruments as in standard Mars science Imaging on 5 orbits in standard Mars MAG, LPW, SEP on on 10 orbits:
science on 7 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 a tude 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 Jet Propulsion Laboratory California Institute of Technology Science Observa ons* - MRO Pasadena, California *Conducted only if safe, posing no spacecraft or instrument issues Mars Exploration Program Office
C/SS Nucleus Closest Approach Possible Encounter with C/SS Debris - 2 days - 1 day + 1 day + 2 days
Periodic C/SS Observa ons each 2hr orbit C/A Periodic C/SS Observa ons on each 2hr orbit
MRO Example Center me for C/SS par cle C/SS C/A encounter with Mars: 20:07 ± 10 min UT 18:31 UT 17:39:30 16:38:26 19:43:51 20:46:49 18:12:16 19:01:52
C/A – 1 orbit: C/A orbit: C/A + 1 orbit: 2 CRISM + 13 HiRISE scans 2 CRISM + 10 HiRISE scans + CTX R/A 2 CRISM + 13 HiRISE scans Various line mes to provide Shortest line mes for best Various line mes to provide different exposures; CTX R/A resolu on; MCS obs of coma (TBD) different exposures, CTX R/A
Key: C/A = Closest Approach; R/A = Ride-Along Nadir observa ons C/SS observa ons 10 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Science Observa ons* - Mars ODY Pasadena, California Mars Exploration Program Office
• Objec ve: – Emphasis on the unique contribu ons to be made by THEMIS: moderate resolu on infrared spectral imaging. • THEMIS: 3 proposed, priori zed observa ons: – 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 en re 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. • Neutron Spectrometer and HEND: – Nominal observa ons while in nadir-point a tude to monitor effects on neutral and charged par cle fluxes.
11 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of TechnologyScience Observa ons* - Opportunity & Curiosity Pasadena, California Mars Exploration Program Office
• 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.
12 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Next Steps Pasadena, California Mars Exploration Program Office • Phasing Maneuvers Ø July 2 MRO 1st of 2 phasing maneuvers (OTM 37) Ø August 5 ODY phasing maneuver, if required Ø August 27 MRO 2nd of 2 phasing maneuvers (OTM 38) Ø October 9 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