Return to the Moon with LCROSS and LRO

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LCROSS

• Our latest mission to the surface of the Moon.
• Developed and managed by NASA Ames Research
  Center in partnership with Northrop Grumman.
• Goal to test whether or not water ice deposits
  exist on the Moon.

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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!
• Carrying water to the Moon will be expensive!
• Learning to Live off the landwould make human
  lunar exploration easier.

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Early Evidence for Water
Clementine
Lunar Prospector
Two previous missions, Clementine (1994) and
Lunar Prospector (1999) gave us preliminary
evidence that there may be deposits of water ice
at the lunar poles.
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Clementine bistatic radar - 1994

• Circular polarization ratio (CPR) consistent with
  ice crystals in the south polar regolith.
• Later ground-based studies confirmed high-CPR in
  some permanently-shadowed craters.
• However, Arecibo scans have also found high-CPR
  in some areas that are illuminated, probably due
  to surface roughness.
• Are we seeing ice or rough terrain in dark polar
  craters?

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Hydrogen has been detected at the poles by Lunar
Prospector in 1999. Is it water ice???
Lunar Prospector neutron spectrometer maps of the
lunar poles. These low resolution data indicate
elevated concentrations of hydrogen at both
poles it does not tell us the form of the
hydrogen. Map courtesy of D. Lawrence, Los Alamos
National Laboratory.
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Lunar Prospector Impact July 31, 1999

• South pole impact at end of mission
• Low angle (6.3), low mass (161 kg), and low
  velocity (1.69 km/s) less than ideal for water
  ice detection.
• No water detected.
• Results not conclusive.

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New Evidence for Water
Deep Impact
Cassini
Chandrayaan-1
Data from 3 other probes has now shown that small
amounts of water are widespread across the
surface of the Moon. The amount of water may
change during the course of the lunar day.
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Where did we look?
Cabeus
JPL/Goldstone Radar Image
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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. The crater floors are very
cold with temperatures of -238 C (-397 F, 35
K), so water molecules move very slowly and are
trapped for billions of years.
Clementine Mosaic - South Pole
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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.
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Where could water ice come from?
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.
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Our Latest Lunar Missions
Lunar Crater Observation and Sensing
Satellite LCROSS
Lunar Reconnaissance Orbiter LRO
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Lunar Reconnaissance Orbiter

• LROC image and map the lunar surface in
  unprecedented detail
• LOLA provide precise global lunar topographic
  data through laser altimetry
• LAMP remotely probe the Moons permanently
  shadowed regions
• CRaTER - characterize the global lunar radiation
  environment
• DIVINER measure lunar surface temperatures
• LEND measure neutron flux to study hydrogen
  concentrations in lunar soil

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LRO Mission Overview

• On-board propulsion system used to capture at the
  Moon, insert into and maintain 50 km mean
  altitude circular polar reconnaissance orbit
• 1 year exploration mission followed by handover
  to NASA science mission directorate

Lunar Orbit Insertion Sequence
Commissioning Phase, 30 x 216 km Altitude
Quasi-Frozen Orbit, Up to 60 Days
Polar Mapping Phase, 50 km Altitude Circular
Orbit, At least 1 Year
Minimum Energy Lunar Transfer
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LCROSS Mission Concept

• Impact the Moon at 2.5 km/sec with a Centaur
  upper stage and create an ejecta cloud that may
  reach over 10 km about the surface
• Observe the impact and ejecta with instruments
  that can detect water

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Excavating with 6.5-7 billion Joules

• About equal to 1.5 tons of TNT
• Minimum of 200 tons lunar rock and soil will be
  excavated
• Crater estimated to have 20-25 m diameter and
  3-5 m depth
• Similar in size to East Crater at Apollo 11
  landing site

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LCROSS Mission System

• Shepherding Spacecraft guided and aimed the
  Centaur to its target and carried all of the
  critical instrumentation.
• CentaurUpper Stage provided the thrust to get
  us from Earth orbit to the Moon and was then used
  as an impactor.

14.5 m
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Save and Time by Using an Existing Structure
Designed to Carry Heavy Payloads During Launch
Put LRO on top
EELV Secondary Payload Adapter or ESPA Ring
Use ESPA ring to make LCROSS spacecraft
Attach bottom of ESPA Ring to top of rocket
But how do you make a spacecraft out of something
that looks like a sewer pipe?
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Answer Put Equipment Around the Rim and Tank in
the Middle
Solar Array
Integrated LCROSS Spacecraft
Propellant Tank
ESPA Ring
Equipment Panel (1 of 5)
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Different Panels Perform Different Functions
Solar Array
LCROSS Viewed From Above without Insulation
Batteries
Science Instruments
Command and Data Handling Electronics (including
computer)
Power Control Electronics
Attitude Control and Communications Electronics
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Panel Approach Makes LCROSS Easier to Put Together
LCROSS with Panels Laid Flat for Integration of
Electronics
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Other Equipment Includes Two Types of Antennas to
Talk Back to Earth
Omni (Low Gain) Antenna (1 on each side)
Medium Gain Antenna (1 on each side)
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And Sensors to Determine Spacecraft Attitude
(Pointing)
Sun Sensors (10 total)
Star Tracker
Solar Array
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Propulsion System Must Maneuver and Point the
Spacecraft
5 lb Thruster for Maneuvers (1 of 2)
Propellant Tank (40.85 dia)
Post Supports Thrusters (1 of 4)
1 lb Thruster for Attitude Control (1 of 8)
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Launch June 18, 2009

• Both LCROSS and LRO shared space aboard an Atlas
  V launch vehicle.
• Launch occurred at Cape Canaveral.

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Launch Vehicle

• We used the Atlas V Launch Vehicle.
• This is the latest version in the Atlas family of
  boosters.
• Earlier versions of Atlas boosters were used for
  manned Mercury missions 1962-63.
• Atlas V has become a mainstay of U.S. satellite
  launches.
• NASA has used Atlas V to launch MRO to Mars in
  2004 and New Horizons to Pluto and the Kuiper
  Belt in 2006.

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Launch Site

• Launch was from Space Launch Complex 41 (SLC-41)
  at Cape Canaveral.
• Historic site where many previous missions
  launched
• Helios probes to the Sun
• Viking probes to Mars
• Voyager planetary flyby and deep space probes
• Mars Reconnaissance Orbiter
• New Horizons spacecraft to Pluto and Kuiper Belt

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When?

• LRO/LCROSS launched June 18, 2009.
• This led to impact at 1130UT on October 9 for
  LCROSS.
• Impact targeted the South Pole region of the
  Moon.

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Centaur-LCROSS-LRO at TLI
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LRO Separation
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LCROSS Lunar Flyby L 5 days
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Lunar Flyby June 23, 2009
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LCROSS Trajectory The Long and Winding Road

• Flyby transitioned to Lunar Gravity Assist Lunar
  Return Orbits (LGALRO).
• 3 LGALRO orbits about Earth (36 day period).
• Long transit also provided time to vent any
  remaining fuel from Centaur.

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LCROSS taken through Liverpool 2-meter Telescope,
La Palma, Canary Islands Robert Smith
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LCROSS in flight taken through an amateur 16-inch
telescope Paul Mortfield
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LCROSS in flight taken through an amateur 16-inch
telescope Paul Mortfield
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LCROSS Separation Impact - 9 hrs 40 min
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Centaur Impact
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Centaur Impact
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Into the Plume

• During the next 4 minutes, the Shepherding
  Spacecraft descended into the debris plume,
  measured its composition, and transmitted this
  information back to Earth.
• The Shepherding Spacecraft then ended its mission
  with a second impact on the Moon.

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Cabeus as Seen From LCROSS
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Centaur Impact From LCROSS
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Centaur Impact Plume
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Centaur Impact Plume
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Centaur Impact Crater
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Centaur Impact Crater
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LCROSS
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Water Signatures Detected!
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OH Also Detected!
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So How Much Water?

• At least 100kg or about 25 gallons seen in
  spectra of impact
• First estimates for total in permanently-shadowed
  areas are about 1-2 of the volume of the
  Great Salt Lake
• 50-100 billion gallons!
• Amount will be refined by
• measurements from LRO.

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New Questions to Answer

• Where did the water come from?
• How long has it been there?
• What kinds of processes have been involved in
  putting it there, modifying it, and removing it?

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Questions