LCROSS Mission Overview & Results (
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Transcript of LCROSS Mission Overview & Results (
LCROSS “the lunar hitch-hiker that made an impact(literally!) on how we
view our Moon and its science secrets”
Dr. Kimberly Ennico (NASA Ames Research Center) poses with LRO (silver), LCROSS (gold), Astrotech, Titusville, FL, May 2009)
LCROSS...at a glance...
Launch: June 18, 2009 Impact: October 9, 2009
(LCROSS was required to meet a 28 month, ATP to launch, schedule, and to have minimal impact to LRO development and launch.)
Why LCROSS?
Mission Primary Objective:
(Classic Scientific Method)
To test whether or not water ice deposits exist on the Moon.
Why Look for Water?
• Humans exploring the Moon will need water:– Option 1: Carry it there*– Option 2: Use water that
may be there already
• Learning to “Live off the land” could make (long-term) human lunar exploration easier.
(*At $10K/lb to orbit. $3-5K more to Moon. At 8 lbs/gallon, it could cost >$100,000/gallon of water to the Moon.)
Early Evidence of Water
Two previous missions, Clementine and Lunar Prospector gave us preliminary evidence that there may be deposits of water ice at the lunar poles.
Clementine(1994)
Lunar Prospector(1999)
Clementine bistatic radar – 1994Ref: Nozette, S. et al. Science 274, 1495-1498 (1996)
• Circular polarization ratio (CPR) consistent with ice crystals in the south polar regolith.
• Ground-based studies (Arecibo) confirmed high-CPR in some permanently-shadowed craters.– However, Arecibo scans also found high-CPR in some areas that are
illuminated, probably due to surface roughness.
Ref: Stacy, N. et al. Science, 276, 1527-1530 (1997)
Controversial: ice or rough terrain?
Lunar Prospector – Hydrogen 1998Ref: Feldman, W.C. et al. Science 281, 1496-1500 (1998)
• Neutron spectrometer maps of both lunar poles• Low resolution data indicate elevated concentrations of hydrogen at
both poles• It does not tell us the form of the hydrogen
Accepted, not conclusive re: ice
Map courtesy of D. Lawrence, Los Alamos National Laboratory.
The “Famous” LP maps
Feldman, W.C. et al. Science 281, 1496-1500 (1998)Map courtesy of D. Lawrence, Los Alamos National Laboratory.
(dark blue/purple <-> low # neutrons <-> high hydrogen <-> water?)
Hi-Res Arecibo & Green Bank radar – 2005Ref: Campbell, D.B. et al. Nature, 443, 835-837 (2006)
• Higher spatial res. (20 m) than 1994 Clementine & 1992 Arecibo data (125 m)
• Surveyed south pole and nearside to latitude ~65° S
• Data indicate correlation between areas of high CPR with walls and ejecta deposits– Shackleton had same CPR values as
Schomberger A&G, and many other young craters
– High CPR areas in Shackleton are in both permanent shadow and seasonal illumination
• Conclude high CPR in Shackleton is not due to ice deposits– But they conclude they are open to
possibility very low abundance (1-2% by mass) mixed in grains from the upper 1 m of regolith
Evidence against ice lakes at poles
Radar image Moon South Pole(left) OC 100m; (right) CPR 500 m
Fig1 from Campbell, D.B. et al. Nature, 443, 835 (2006)
Selene (Kaguya) Terrain Camera – 2007Ref: Haruyama, J. et al. Science, 322, 938-939 (2008)
• Terrain Camera (10 m res.) surveyed inside Shackleton Crater– Targeted during lunar mid-summer to get
max. illumination of the shadowed regions by sunlight scattered off nearby higher terrains
– Discovered small craters on inner wall (100’s m dia.), mount-like features (300-400m thick), & central hill (200m height)
• Derived temperature measurement of Shackleton floor ~88 K (max)– Cold enough to retain water-ice
• Did not find bright areas in Shackleton that could be due to pure water-ice– Looking for albedo ~1.0
• They also conclude they are open to possibility very low abundance (1-2% by mass) mixed in grains from the upper 1 m of regolith
Evidence against ice lakes at poles; temperature is cold enough to support ice
How could there be water at the lunar poles?
• The Sun never rises more than a few degrees above the polar horizon so the crater floors are in permanent shadow (PSR).
• The crater floors are very cold with temperatures < -200° C (70K, -328° F), so water molecules move very slowly and are trapped for billions of years.
Many orbits Clementine data South Pole (Ben Bussey, APL)
(On October 9, 2009, LCROSS performed the first “in-situ” study of a PSR.)
Where could water ice come from?
• Over the history of the Moon, when comets or asteroids impact the Moon's surface, they briefly produce a very thin atmosphere that quickly escapes into space.• Any water vapor that enters permanently shadowed craters could condense and concentrate there.
(volatiles from comets, asteroids, IDPs, solar wind, GMCs, the Moon itself!)
• Water molecules at lower latitudes may form from interactions with hydrogen streaming out in the solar wind. • These water molecules may get baked out of the lunar soil and can then get trapped in polar craters.
How much water could there be?
• There is ~12,500 km2 of permanently shadowed terrain on the Moon.
• If the top 1 meter of this area were to hold 1% water (by mass)*, that would be equivalent to about 4.1 x 1011 liters of water!
• This is approximately 2% the volume of the Great Salt Lake in Utah.
(*The Sahara desert is 1.2% water (by mass) in its top 20cm, with 2.5-4.5% at 3m.)
Enter LCROSS-The pathfinderLCROSS had a challenging set of
constraints:• We had to fit within 1000Kg wet
mass…• We had to design and build the
payload, spacecraft and mission in only 30 months!
• We had a cost-cap of $79M, including reserves…
• We couldn’t levy any requirements on LRO…
• As a NASA Class D mission some programmatic and technical simplifications could be leveraged
The LCROSS Experiment
• Impact the Moon at 2.5 km/sec (5,600 mph) with a ~2366 kg (5216 lb) Centaur upper stage and create an ejecta cloud into the sunlight for observation
• Observe the impact and ejecta with instruments that can detect water
• Four minutes later the ~625 kg (1378 lb) LCROSS S/C itself impacts at 2.5 km/s
Flash~0.1 min
Curtain3.0 min
Crater1 min
Excavating with 6.5-7 billion Joules
• About equal to 1.5 tons of TNT• Minimum of 200 tons lunar rock and soil expected to be excavated• New crater estimated to have ~20-25 m diameter and ~3m depth• Similar in size to East Crater at Apollo 11 landing site
Anatomy of an Impact – flash, curtain, crater
“Sunrise”
Reverse ejecta
Crater rimIncandescent particles
Nadir View of Impact and Ejecta CurtainImpact flashImpact flash
Ejecta Curtain Into
sunlight
Ejecta Curtain Into
sunlight
Tim
e
Tim
e
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
ARC Vertical Gun Experiments
Scales to ~2 sec after Centaur impact
Pete Schultz
Recent “Controlled” Lunar Impacts
S/C Impact Date S/C Mass S/C Velocity at impact
Impact angle from
horizon.
Impact Location Observations
Hiten/Muses
10 Apr 1993 143 kg 2.33 km/s 42° 55°E, 32.4°S Flash (hydrazine)
LP 31 Jul 1999 161 kg 1.69 km/s 6.3° South pole area Null
SMART-1 3 Sep 2006 285 kg 2 km/s 1° 46.2°W, 34.4° S Flash, plume
Change’1 1 Mar 2009 2350 kg ? ? just south of the lunar equator, at
52.36 degrees East Longitude
?
Kaguya (Selene)
10 Jun 2009 ~1800 kg 1.8 km/s 1° 80.4°E, 65.5°S Flash
LCROSS 09 Oct 2009 2366 kg 2.5 km/s >85 ° 48.703°W, 84.675°S; Flash, Plume, Crater
LCROSS S-S/C
09 Oct 2009 625 kg 2.5 km/s >85 ° 48.703°W, 84.675°S; Null (to date)
Why LCROSS would be different….
0
50
100
150
200
250
300
350
400
0 20 40 60 80
Impact Angle (degrees)
Ejecta Mass (Metric Tones)
LCROSSSMART-1LPLCROSS S-S/C
SMART-1 (grazing impact)
LP
LCROSS Centaur
LCROSS S-S/C
SMART-1 (hill side impact)
NOTE: LCROSS Predictions shown. LP/SMART-1 actuals shown
ARC Vertical Gun Experiments
LCROSS was an artificial impactor(natural impacts* happen all the time)
(*Natural impacts typically have much more energy than LCROSS’s 6-7e9 Joules.)
Ref: Montañés-Rodríguez, Pallé, & Goode, AJ, 134, 1145-1149 (2007)NASA Marshall Lunar Impact Monitoring Program http://www.nasa.gov/centers/marshall/news/lunar/
The LCROSS Mission Recipe
• Step 1: Hitch a ride to the Moon• (Thanks LRO)
• Step 2: Part with LRO, but hang onto that rocket!• (we’ll use it later)
• Step 3: Tug it around the Earth• Step 4: Point it toward our crater• Step 5: Let go!• Step 6: Slow-down & watch what kicks-up• Step 7: Send pics & data back to Earth• Step 8: Say good-bye
• (Taste regolith!)
The LCROSS Mission ConceptLaunched stacked with LRO June 18, 2009
After Lunar swing-by, enter a 4 month cruise around Earth
October 9, 2009, target the Centaur Upper Stage and position S-S/C to fly 4 minutes behind
S-S/C observes impact, ejecta cloud and resulting crater, making measurements until impacting itself
1. 2.
3. 4.
Spacecraft & Impactor
Secondary Payload ApproachLCROSS literally hitched a ride to
the moon!
(LCROSS was required to meet a 28 month, ATP to launch, schedule, and to have minimal impact to LRO development and launch.)
Delta II
Atlas V
When LRO upgraded to a larger launch vehicle, there was an extra 1kg launch mass available.
http://www.nasa.gov/mission_pages/LCROSS/multimedia/gallery/
Secondary Payload Approach
Secondary Payload Approach
http://www.nasa.gov/mission_pages/LCROSS/multimedia/gallery/
“Creativity Loves Constraints”LCROSS’ Innovative Approach
Re-use of upper-Centaur stage as the
2300kg impactor
Turn the ESPA ring into the actual spacecraft mechanical structure
Spare Tracking Data Relay System satellite propellant tank
Petal-like panels fold up and down during I&T, eased access
http://lcross.arc.nasa.gov/spacecraft.htm
“Creativity Loves Constraints”Leveraged Technology
Shares the same build-to-print avionics suite as LRO
NG Flight Software Heritage, using 10 year old code, just updated
Propulsion System uses all commercially available parts
Star Tracker & IRU & ACS FSW similar to LRO’s arrangement
http://lcross.arc.nasa.gov/spacecraft.htm
“Creativity Loves Constraints”COTS Payload
Kimberly Ennico & Mark Shirley testing the LCROSS payload at NASA ARC (left) and NGST (right)
Mission Day 0 (09-169; Jun 18)Launch! 5:32pm EDT
Mission Ops Center NASA Ames Launch from Cape Canaveral, FL
Fairing separation
LCROSS star tracker
Fairing
Earth
Where’s LCROSS?
LCROSS taken through Liverpool 2-meter Telescope, La Palma, Canary Islands – Robert Smith
LCROSS in flight taken through an amateur 16-inch telescope – Paul Mortfield
LCROSS in flight taken through an amateur 16-inch telescope – Paul Mortfield
Where’s LCROSS?
Where’s LCROSS?
Where’s LCROSS?
http://www.lewislearning.org/
Mission Day 4 (09-173; Jun 22)Starfield Calibration
Angular distance between Aquila (Altair) and Aquila (Tarazed) on the sky is 1.86 degrees and was measured to be 46 pixels (along the diagonal) on NIR2. This confirmed a platescale of ~1.89/46 = 0.04 degrees/pixel for NIR2 (at least within the central region of the array).
Mission Day 5 (09-174; Jun 23)Lunar Swingby
Ennico, et al. (2009)
Mission Day 5 (09-174; Jun 23)Lunar Swingby
(This was the scene of Lunar Swingby, June 23, ~2:30am.)
Tony Colaprete (maroon shirt), reviews live data, Kim Ennico (black shirt) in front compares live data to expected performance using checklists. Jen Heldmann (in back) updates STK viewpoint for live streaming test.
Mission Day 44 (09-213; Aug 01)Earth Calibration at 360,000 km
North
North
NIR1
NIR2
MIR1*
MIR2 Full Earth at 360,000km
O3
O3
H2O
O2
H2O
H2O
CO2
CO2 CH4
Ennico, et al. in prep.
Mission Day 60 (09-229; Aug 17)Earth Calibration at 520,000 km
Crescent Earth at 520,000km. Crescent Moon at 881,000 km.
Mission Day 92 (09-261; Sep 18)Earth Calibration at 560,000 km
STK Boresight Map
Quarter-Earth at 560,000 km
NIR1 (1.4-1.7um) NIR2 (0.9-1.7um) MIR1 (6.0-10um) MIR2 (6.0-13.5um)
Ennico, et al. in prep.
Mission Day 113 (09-282; Oct 09)Separation
MIR_S1_W0000_T3425953m305
d = 300 md = 150 m
MIR_S1_W0000_T3425736m453
MIR_S1_W0000_T3426668m025
d = 800 m
Cam6_W0000_T3425736m969
d = 150 mEnnico, et al. (2009)
Mission Day 113 (09-282; Oct 09)Separation
Buie & Ryan, SWRI & Magdalena RidgeCentaur Light curves observed from Earth 3-5 hrs before impact
Mission Day 113 (09-282; Oct 09)Impact!
(This was the scene of Impact at the Science Ops Center, Oct 9, ~4:30am.)Tony Colaprete (black shirt), reviews live data, Kim Ennico (maroon shirt) on voice command to MOS to command camera
change request based on live data analysis by Tony & Kim (on the fly).
Where did we go and why?
Target Selection Criteria:1. Ejecta Illumination
2. Association with hydrogen
3. Observable to Earth
4. “Smooth”, flat terrain
Final decision considered available data, status of LCROSS payload, ability of LRO to observe, and limits of Earth observing for each site.
LCROSS Visible Camera Image 2009-09-09 11:00 UTC
•
Cabeus Crater
Where did we go?
http://www.nasa.gov/mission_pages/LCROSS/main/candidate_craters_story.html
X
Goldstone map
Where did we go?
http://www.nasa.gov/mission_pages/LCROSS/main/candidate_craters_story.html
X
Goldstone map
Where did we go?Cabeus A:• Best Earth observing (not perfect since backdrop would have been lit moon)• Hydrogen association was questionable
Cabeus B:• No obvious association with hydrogen
Cabeus:Obvious hydrogen, but worst Earth observing
(Viewpoint from LCROSS, Oct 9)
LCROSS Visible Camera Image 2009-09-09 11:30 UTC
Target Crater CabeusTarget Crater Cabeus
Where did we go?
(Viewpoint from Earth, Oct 9)Nancy Chanover, APO
Expected Plume Area
Where did we go?
(Viewpoint from Earth, Oct 9)Nancy Chanover, APO
Where did we go?
(Target area with good elevation angles to Sun for ejecta illumination. Source: LRO LOLA.)
How Close Did We Hit?
(We hit within 100 meters of our predicted target!)
Marshall, W., Shirley, M. et al. in prep.
So... Why no big plume?
Predicted What we think we didSchultz, et al (2010)
What did we see?
(Observed expanded ejecta cloud 10-12km in diameter at 20s after impact. Visible camera imaged curtain at t+8s through t+42s, before cloud dropped below sensitivity range).
Schultz, et al (2010)Cam1_W0000_T3460421m473
t+0s
What did we see?
(Thermal signature seen in mid-IR cameras t+2-10s believed to be impact-heated ballistic ejecta that did not get into sunlight (low-angle plume). Ejecta after 4s is within a single pixel, ~1km/pix at this altitude.)
MIR_S1_W0000_T3460402m651.png MIR_S1_W0000_T3460404m653.png MIR_S1_W0000_T3460406m655.png
t+6s
t+2s t+4s
t+8s t+10s
MIR_S1_W0000_T3460408m657.png MIR_S1_W0000_T3460410m659.png MIR_S1_W0000_T3460412m159.png
Multi-pixel signature >1km structure
View of Moon from Earth on 9 October 2009, 4:30 a.m. PDT
Coordinating Observations
Coordinating Observations
A Coordinated Professional Observation Campaign using Earth, Earth-Orbit and LRO has been part of the mission from the start.
http://groups.google.com/group/lcross_observation?hl=en
Backyard astronomer observations are coordinated through the LCROSS Google Group
Coordinating Observations
Other EyesCanada France Hawaii Telescope (Hawaii)Apache Point Observatory (New Mexico)Infrared Telescope Facility (IRTF, Hawaii)MMT Observatory (Arizona)Magdalena Ridge Observatory (New Mexico)Keck (Hawaii)Gemini North (Hawaii)Subaru Telescope (Hawaii)Korea Astronomy & Space Science Institute (Arizona & Korea)Mount Wilson (California)Air Force AEOS Telescope (Hawaii)Allen Telescope Array (California)Palomar Observatory (California)Lick Observatory (California)
Hubble Space Telescope, Lunar Reconnaissance OrbiterOdin, IKONOS, GeoEye-1
LCROS EBOC Campaign
NASA GSFC
Coordinating Observations
Coordinating Observations
Apache Point Observatory (New Mexico)
Nancy Chanover, APO
Coordinating Observations
Keck guider image (Mauna Kea, Hawaii)
Wooden, et al.
Coordinating Observations
Canada France Hawaii Telescope
Christian Veillet, CFHT
Coordinating Observations
BEFORE
AFTER
MMT Observatory, Arizona
Faith Vilas, MMT
Coordinating Observations
LCROSS Water Measurement
New Lunar Water Evidence (?)- 2009
Data from these probes has shown that small amounts of waterare widespread across the upper millimeter surface of the Moon. The amount of water may change during the course of the lunar day.
Deep Impact CassiniChandrayaan-1
Clark, et al (2009), Pieters, et al (2009), Sunshine, et al (2009)
Must excavate
1 ton regolith to get 32oz (0.25 gal) ‘water.’
(1000 ppm)
The measurement...
LCROSS’ (different) water measurement
Model a 230°C (500K) greybody...
LCROSS’ (different) water measurement
Add to it a water model...
H2O
H2O H2O
LCROSS’ (different) water measurement
Add in some other simple molecules...
H2O
H2O H2O
OtherOther
LCROSS’ (different) water measurement
So... How Much water?• LCROSS (Colaprete, et al 2010)
– sampled one area, created a 20-30m diameter crater, excavated ~250 metric tons (from model)
– only observed 2202-4382 kg sunlit material (above 833m alt) at impact+8s.– two band depths measured
• H2O (1.4 & 1.8um) -> 145 kg H2O vapor+ice• OH (308-310nm) -> 110 kg H2O vapor+ice
– model dependent (mixing) -> mean water concentration 7.4 wt% ± 5.4 wt%– observed 688-1369 kg sunlit material at impact +30-200s
• LAMP/LRO (Hurley, et al. 2009)
– observed H2, peak column density ~158kg H2 released, – fit models -> <400 kg H2O released, – assumed 20,000kg was released -> <2% wt%
• LEND/LRO (Mitrofanov, et al. 2010)– 2100-5400 ppm measurements -> 1.9-4.9 wt%
• Diviner/LRO (Hayne, et al. 2010)
– observed 760-1800 kg sunlit material at impact +90s
M3 “0.25 gal H2O/1 ton soil”; LCROSS “10 gal H2O/1 ton soil”
In Summary (1 of 3)
• LCROSS proved that a new class of mission (NASA Class D) high science payoff at low cost/high risk is possible
• Tight schedule & budget constraints (or you would lose your ride) forced proactive and rigorous project management with very visible risk management
• Lifecycle of “cradle to grave” in <3 years excellent training experience
• Design engineers used as part of ops team was essential in quick turn-around response to anomalies and events
• Ruggedized-COTS instruments did perform well in space (~5-10 hrs operation time), high performance at low cost
• Never underestimate the importance of on-orbit calibration data (saved our bacon)
In Summary (2 of 3)
• Impact appears to have occurred in a volatile rich area:
• Water …and other stuff!! (e.g., CH4, CO2, SO2, NH3, Na, K, CO, NH2) possibly observed…work occurring now to get unique identification
• Band depths and OH emission strengths indicate significant amounts of water (>150 kg vapor and ice)– Reported concentration: 7.4 wt% ± 5.4 wt% (Colaprete, et al. 2010)
– From LEND: ~ 1.9 - 4.9 wt% (for 3 cm dry layer) (Mitrofanov, et al. 2010)
– Remember, ESMD requirement for moon base was 1 wt%• The amount and types of volatiles suggest:
– The very cold temperatures sequester all sorts of volatiles (see Zhang & Paige, 2009)
– Need multiple source model (see Lucey, 2000)
In Summary (3 of 3)
Science can be surprising!
Prediction What may have happened...
Updates on the LCROSS mission results are posted at http://www.nasa.gov/LCROSS
http://lcross.arc.nasa.gov
LCROSS Papers/Presentations
Lunar Exploration Analysis Group (LEAG), November 17-19, 2009, Houston, TX (Impact +1 m)Colaprete et al.,Schultz et al.,Heldmann et al., Wooden et al.,
American Geophysical Union (AGU), December 12-16, 2009, San Francisco, CA (Impact +2 m)Colaprete et al.,Schultz et al.,Chin et al.,McClanahan et al.,Hermalyn et al.,Ennico et al.,Heldmann et al.,Wooden et al.,Hurley et al.,
Submitted to Science, Jan 2010 (Impact + 3m)Colaprete et al.,
Schultz et al.,Hayne, et al.
Goldstone et al. Mitrofanov, et al.
Lunar and Planetary Science Conference, March 1-5, 2010, Houston , TX (Impact +5 m)Seven (7) oral and eleven (11) poster presentations in Special Session: “A New Moon: LCROSS,
Chandrayaan Chang'E-1 Results”