deep impact/epoxi status and plans · targeting ellipse target asteroid b t – m b r – m flyby...

National Aeronautics and Space Administration!Jet Propulsion Laboratory!California Institute of Technology!

SBAG January 14-16, 2013

Deep Impact/EPOXI Status and Plans

T. Larson, M. A’Hearn, S. Chesley


Deep Impact

SBAG, January 14-16, 2013 2

Launch 01/12/2005

9P/Tempel 1 Impact 07/04/2005

103P/Hartley 2 Flyby 11/04/2010


Since Hartley 2

•  Observation campaign of comet Garradd (C/2009 P1) in Spring of 2012 •  Gravitational microlensing demonstration campaign during Summer of

2012 –  Data analysis under way (Dave Bennett – Notre Dame)

•  Senior review proposal for FY13&14 not approved •  Faced team shut down and long term hibernation starting Fall 2012 •  Discovery Program Exec provided funding to delay hibernation and

enable initial imaging campaign for comet ISON –  Visible light images and IR spectra to be collected Jan 17 – March 10

•  Currently operating s/c with 1 full time engineer and scattered part time support

•  Second pre-perihelion opportunity to image ISON in July-August 2013 –  Funding for this is TBD



Future Opportunities

•  More ISON imaging opportunities (post-perihelion) in 2014 •  Deep Impact is uniquely positioned to view comet 67P/Churyumov-

Gerasimenko while Rosetta is deep inside the coma near the nucleus –  Essentially unobservable from earth –  DIF has 7 month view period in 2015

•  TCMs performed in 2011 and 2012 put DIF on course for a flyby of PHA 2002 GT in January 2020

•  Additional bright comet observation opportunities •  No funding is yet committed for any of these

–  Availability of FY14 funding is TBD –  C-G and 2002 GT are in future senior review proposal periods



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C/Garradd (C/2009 P1) •  Intrinsically active, therefore bright & widely observed •  Dynamically very young

–  (1/a)0=0.000397 •  Two windows for DIF (post-perihelion)

–  Feb-Apr 2012, r~2.0 & Δ~1.9 AU - vis & IR data, next slide –  Jul-Aug 2012, r~3.2 & Δ~2.9 AU - no ops

•  Data-taking severely limited by lack of DSN downlink availability (s/c is far from Earth so bandwidth is low)

•  Spectral results now using latest recalibration of IR spectrometer

•  Similarly no observations of C/PanSTARRS


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Vis Camera Results •  Coma structure amorphous – no jets

•  Rotational light curves from broad-band visible (dust) and from narrow band CN (gas)

•  Amplitude only few% (1% in dust)- enabled by stable environment and 24-hour coverage

•  Only measured period for this comet: P=10.42±0.04 hr

•  Release of CN and OH consistent with ground-based measurements with additional information on rotational variation

•  Bodewits, Farnham, & A’Hearn CBET 3090


Spectrum of Garradd •  Q(H2O)/Q(CO2)/Q(CO) =

1.0/0.08/0.6 –  Optically thick model in red

•  Note detection of what is likely OH

–  Not usually observed in IR but not unexpected

•  CO2 fraction “normal” –  5% < 8% < 25% –  Only one measurement – no

other facility can measure CO2

•  Higher CO/H2O than any previous observer of Garradd –  Q(CO) increases

systematically around orbit!! –  Totally unexpected behavior

•  Don’t know which species CO2 follows 7


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Variation Along Orbit


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•  CO in nucleus is not correlated with H2O

–  Certainly not in release from nucleus

•  Spatially separate originally?

•  Or only as a result of selective release?

•  Excess of CO from cosmic ray irradiation of CO2 below sublimation front?

•  Is this typical of dynamically new and/or very young comets? Not like C/Hale-Bopp (dynamical age uncertain)

•  Another example of new cometary behavior (totally unlike best studied previous comet) discovered with DIF

New Insights - Garradd

National Aeronautics and Space Administration!Jet Propulsion Laboratory!California Institute of Technology! DIF Windows for ISON

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Date Range Heliocentric Distance

S/C Range App Mag

2013 Jan 5 – Mar 8 5.2 - 4.5 5.6 - 3.9 17 - 15

2013 Jul 7 – Sep 10 3.0 – 2.0 2.2 – 2.3 12 - 10

2014 Mar 7 – May 4 2.3 – 3.2 2.6 – 2.5 11 - 13

2014 Aug 29 – Nov 23 4.6 – 5.5 3.9 – 6.0 15 - 17

Only first window is funded! Observations start 17 Jan! UM still working “on spec”


DIF Contributions

•  Pre-Perihelion •  Window 1:

–  1st determination of rotational period critical for understanding breakup (if it happens)

–  CO or CO2 hyperactivity?

•  Window 2: –  Abundances of H2O & CO2 &

CO? –  Slope of activity variation

needed for perihelion predictions & physical model

•  Post-Perihelion •  Window 3:

–  Asymmetry around perihelion; needed for evolutionary models near sun

–  Abundances (H2O, CO2, CO) needed for physical models

•  Window 4: –  Asymmetry & outbound

slope needed for physical models

–  Changes in rotational period

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National Aeronautics and Space Administration!Jet Propulsion Laboratory!California Institute of Technology! Why Does it Matter?

•  DI is only platform able to measure CO2, a key volatile that drives the activity in some comets. Must understand volatiles at larger distances to understand transitions in behavior at small r

•  DI has demonstrated (C/Garradd) ability to determine rotational periods from very small amplitude activity in coma. Period needed early for interpreting any breakup phenomena at perihelion

•  C/ISON not observable from Earth in window 2 – turn on point for water sublimation

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Deep Impact Flyby of 2002 GT

•  Deep Impact is now on course for Jan. 2020 flyby of a sub-km NEA –  Targeting completed in Oct. 2012, leaving >7 m/s for cruise and flyby targeting

•  Flyby target is 163249 (2002 GT), a PHA ~800 m in diameter –  Orbit and absolute magnitude are both well-constrained, but little else is known

about the body (or bodies) –  Excellent observing circumstances in mid-2013, providing the best opportunity

for pre-flyby characterization •  SMD is supporting characterization effort, but flyby mission is not yet funded

SBAG, January 14-16, 2013 13

Absolute Mag. 18.3

Diameter Est. ~780m (500-1300m)*

Peri- & Aphelion 0.89 x 1.79 AU

Eccentricity 0.33

Inclination 7.0°

Earth MOID 0.015 AU

Taxonomic type Unknown

Spin state Unknown *Assumes albedo range from 0.05-0.35.


2002 GT Characterization Campaign

SBAG, January 14-16, 2013 14

Variety of observing techniques •  Light curves •  Radar •  UV, Vis. & IR spectra •  Vis. & IR flux •  Astrometry

Derived asteroid properties •  Albedo •  Diameter •  Shape & spin state •  Taxonomy/Mineralogy •  Multiplicity

Numerous Observatories Involved Worldwide Santana/GMARS 0.35m Palmer Divide 0.5m Table Mountain 0.6m Ondrejov 0.6m Palomar 1.5m La Silla 1.5m Lulin 1.0m UH 2.2m Magdalena Ridge 2.4m Yunnan 2.4m IRTF 3.0m Kitt Peak 4.0m Palomar 5.1m MMT 6.5m Gemini N 8.1m GranTeCan 10.4m Arecibo 305m


2002 GT Flyby Scenario

The encounter circumstances are listed at right. The phase angle is unfavorable for inbound imaging, and so the team has developed a novel flyby technique whereby the spacecraft will slew to an outbound imaging attitude after the terminal guidance imaging and maneuver activities are complete, approximately 2 minutes prior to encounter. Both Deep Impact cameras, the MRI (10 mrad FOV) and the HRI (2 mrad FOV), will take images continuously until the target is captured in the field post-flyby. After acquisition, autonav will track the nucleus through duration of flyby imaging sequence. The first image will be at a range of 20-50 km, yielding HRI resolutions of 4-10 cm/pixel.

SBAG, January 14-16, 2013 15

Autonav commands slew to follow asteroid as soon as asteroid appears in images.

MRI & HRI res. in cm

Full frame imaging with MRI and HRI.

Asteroid

Flyby distance of 1-2 km

Spacecraft targeting

ellipse

Target Asteroid

BT – m BR

– m

Flyby Details Encounter Date 4 January 2020 Flyby Velocity 7.1 km/s App./Dep. Phase Angle 138/41 deg. Flyby Distance 1-2 km Best Resolution 4-10 cm MRI Full-frame dist. ~78 km Full frame res. ~0.8 m


2002 GT Flyby Science Drivers

•  The geology of asteroids is still poorly understood, especially for sub-km asteroids that are more susceptible to YORP-induced spin up and possible binary formation through fission.

•  The high-resolution flyby imagery will reveal the crater and boulder distribution across the surface and will aid understanding of the distribution and nature of fines on the surface, including size sorting through seismic shaking or electrostatic dust levitation.

•  The existence of features at the scale of the body can indicate the relative importance of cohesive forces.

•  The surface slopes will indicate the extent to which the body’s surface is relaxed and provide an indication of the mechanical properties of the surface material.

•  The overall shape, taken together with size and rotation state, can allow inferences as to the fundamental nature of the body, whether it be monolithic, fractured or a rubble pile.

•  If the object is a binary (~16% probability), the science returns would significantly increase, revealing the mass and density of the bodies and providing the first high-resolution imagery of a binary asteroid system.

SBAG, January 14-16, 2013 16

Hayabusa

Chang’E 2

NEAR-Shoemaker

deep impact/epoxi status and plans · targeting ellipse target asteroid b t – m b r – m flyby...

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