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Principle Investigator Payload Manager

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Title: Principle Investigator Payload Manager


1
Anthony Colaprete
Principle Investigator Payload Manager
2
Workshop Goals
  • What we hope to get out of this workshop
  • Introduce interested parties to LCROSS
  • Provide enough background and insight to help
    frame the observations and stimulate critical
    thinking
  • Identify challenges and opportunities
  • Identify specifics regarding observational
    techniques, methods and instrumentation
  • Identify process for disseminating information
    and support, prior to, during and after the
    impact
  • Hopefully, get excited for a challenging, but
    rewarding observation campaign!

3
Topics
  • Topics covered in this talk
  • Science goals and LCROSS mission rational
  • Overview of the LCROSS mission
  • The anatomy of an impact
  • Expectations What one might expect to see

4
General Science Questions
  • Nature and form of the hydrogen?
  • Water, hydrated minerals, hydrocarbons?
  • Grain size?
  • Distribution within regolith?
  • Nature of PSR regolith?
  • Strength? Depth?
  • Grain size?
  • Composition?
  • Is it similar to Apollo sites?
  • The Lunar Atmosphere
  • How does the Lunar atmosphere respond?
  • What are the times scales for recovery?
  • How do volatiles/dust migrate?

5
LCROSS Mission Objectives
  • The LCROSS mission rational
  • The nature of lunar polar hydrogen is one of the
    most important drivers to the long term lunar
    exploration architecture
  • Need to understand Quantity, Form, and
    Distribution of the hydrogen
  • The lunar water resource can be estimated from a
    minimal number of ground-truths
  • Early and decisive information will aid future
    ESMD and LPRP missions
  • The LCROSS mission science goals
  • Confirm the presence or absence of water ice in a
    permanently shadowed region on the Moon
  • Identify the form/state of hydrogen observed by
    at the lunar poles
  • Quantify, if present, the amount of water in the
    lunar regolith, with respect to hydrogen
    concentrations
  • Characterize the lunar regolith within a
    permanently shadowed crater on the Moon

6
LCROSS Science Background
  • Lunar Prospector detected an increase in hydrogen
    concentration over the lunar poles.
  • The debate over the form, concentration and
    distribution has continued ever since.
  • If the hydrogen in an accessible and usable form,
    it could be a potential resource
  • Form, distribution and concentration of H
    relevant to inner solar system asteroid/comet
    fluxes, lunar volatiles and planetary evolution.
  • Several key questions
  • Is the hydrogen in the form of water?
  • Is the hydrogen diffuse and uniform, or
    concentrated and distributed in pockets?
  • Is the lunar regolith in a permanently shadowed
    crater the same as that characterized at the
    Apollo landing sites?

SP Hydrogen Abundance
Feldman et al., 1998
LCROSS will provide the most unambiguous data set
to address these questions.
7
LCROSS Science Background
Clementine Mosaic - South Pole
How could water be at the lunar poles? The sun
never gets more then several degrees about the
polar horizon, thus topography can provide
permanent shade. Permanently shadowed regions
(PSRs) may have temperatures lt -200 C (-328
F). These PSR will cold-trap most volatiles,
including water, for billions of years. LCROSS
will sample and analyze regolith from a (PSR) by
creating an impact into a PSR (similar to Deep
Impact). The first in-situ study of a PSR
8
Lunar Polar Hydrogen
Deconvolved Hydrogen Maps (Elphic et al., 2007)
Original Lunar Prospector Hydrogen Map (Maurice
et la., 2003)
Water is heterogeneous from one crater to another
? Accumulation/retention processes differ at
carter scales of 50-100 km. Possibly different
at smaller scales.
9
The LCROSS Mission
  • The LCROSS Mission is a Lunar Kinetic Impactor
    employed to reveal the presence nature of water
    ice on the Moon
  • LCROSS Shepherding S/C (S-S/C) directs the 2200
    kg Centaur into a permanently-shadowed crater at
    2.5 km/s
  • gt200 metric tons of regolith will be excavated,
    leaving a crater 20 meters in diameter and 3
    meters deep
  • The S-S/C decelerates, observing the Centaur
    ejecta cloud, and then enters the cloud using
    several instruments looking for water
  • The S-S/C itself then becomes a 700 kg 'impactor'
    as well, impacting 10 km (3s) away from Centaur
    impact.

10
The Mission How LCROSS is Different from LP
Estimates of the total ejecta mass as a function
of impact angle for four impactors LCROSS,
LCROSS S-S/C, Lunar Prospector (LP), and SMART-1
LCROSS
LCROSS S-S/C
SMART-1 (hill side impact)
SMART-1 (grazing impact)
LP
11
LCROSS Mission Animation
( Click green button to start QuickTime movie )
12
The Spacecraft and Payload
Payload Panel
Payload Observation Deck (POD)
13
LCROSS Payload
14
LCROSS Payload The POD
NIR Camera 1 (NIR1)
NIR Camera 2 (NIR2)
Visible Camera (VIS)
Total Luminance Photometer (TLP)
MIR Camera 1 (MIR1)
NSP1 Nadir Fore-Optics
MIR Camera 2 (MIR2)
VSP Nadir Fore-Optics
15
Yours Trulyin Five Wavelengths
NIR 2
NIR 1
Visible
MIR 1
MIR 2
16
SV Being Built at NG
17
The Impact and Crater
SPH Modeling
  • Prospecting with 6.5 Billion Joules
  • Impact predictions drive mission, payload and
    observation design.
  • Both analytical and experimental methods
    employed.
  • Have adapted the mission based on results
  • S-S/C follow time
  • Instrument aperture size
  • Site selection

Radar Imagery (Campbell et al., 2006)
ARC VG Experiments
18
The Anatomy of the Impact Flash, Curtain, Crater
ARC Vertical Gun Experiments
Step 5
Step 1
Impact flash
Nadir View of Impact and Ejecta Curtain
Step 6
Step 2
Time
Time
Step 3
Step 7
Ejecta Curtain Into sunlight
Step 4
Step 8
Scales to 2 sec after Centaur impact
Pete Schultz
19
Impact Studies SPH
The structure / strength properties of the
Centaur matter.
Low density (0.03 g cm-3) Impactor
Vertical Velocity (log v, cm/s)
Maximum Height (log z, cm)
2 meter
2 meter
Martin Jutzi
A low density impactor likely to excavate to only
1.5 m and ejecta about a factor of 5 times less
mass to 2 km altitude, relative to a solid
impactor.
20
Impact Studies SPH
Dumbbell Model for Impactor
Vertical Velocity
Vertical Velocity
Martin Jutzi
Angle at which the centaur hits will make a
difference how it hits can be predicted from
the measured Centaur tumble and may be
discernable from flash. (Note To rise above a 2
km crater rim ejecta will need a velocity 100 m
s-1)
21
Impact Studies SPH
Low End 7000 kg with Vgt100m/s High End 20,000
kg with Vgt100m/s
Martin Jutzi
22
Impact Expectations MC Scaling Studies
90 1.5x104
avg 6x103
med 3.8x103
Don Korycansky
Montecarlo study of ejecta mass Simulation
varied the crater radius (Rcrat), velocity
function exponent (a), total mass (Me), and
ejecta flight angle (q). (See LCROSS technical
note LCROSS ejecta dynamicsMonte Carlo model
(09/16/06) for details)
23
Impact Expectations Curtain Properties
Ejecta Curtain Characteristics Total Curtain
Mass
Altitudes
2 km
5 km
10 km
15 km
25 km
35 km
24
Impact Expectations Curtain Properties
Ejecta Curtain Characteristics 1 water content
Altitudes
2 km
5 km
10 km
15 km
25 km
35 km
Assumes a 30 mm ice grain subliming in 10 sec.
25
Impact Expectations Curtain Properties
Curtain Dust and Water Ice Optical Depth
Curtain Mass and Radius
For Mass above 2 km
For Mass above 2 km
The most observable portion of the ejecta curtain
will be between 10 and 60 seconds after impact,
corresponding to a curtain radius of between 1
and 10 km.
26
Impact Studies - AVGR
Frames from a shot at the Ames Vertical Gun
Range. The shot was meant to mimic what the
LCROSS S-S/C would see and includes
non-uniformities in surface structure (i.e.,
preexisting crates of similar dimension).
Before
After
Pete Schultz
lcross_nov.avi
27
Impact Studies - AVGR
  • Frames from a shot at the Ames Vertical Gun
    Range. The shot was meant to mimic what the
    LCROSS S-S/C would see
  • projectile velocity of 2.5 km/sec
  • a masked target area (equivalent to a 2 km
    crater rim)
  • illumination from the side
  • imaging from above

Impact Direction
Camera
Illumination
Crater Mask
28
Impact Expectations Curtain Shape
Ejecta cloud optical depth modeled with a
truncated conical section, the upside-down
lampshade model. Conical section grows at a rate
which follows the maximum cloud density contour.
t2
Solar Scatter
t1
t
Projected column annulus at time, t
29
Impact Expectations Curtain Radiance
  • To simulate the solar illumination of the ejecta
    curtain a well know (and tested) multi-stream
    scattering code is used (DISORT).
  • Estimates of the ejecta dust and water ice
    optical depths are made based on the expected
    total ejected mass and assumptions of the mean
    particle size and optical properties.
  • Linear mixing is used to combine dust and water
    ice cloud optical properties.

Calculated Backscatter Flux
t, w,g(dust,ice)
30
Impact Expectations Curtain Brightness
Calculated ejecta cloud radiance (left axis, blue
line) and percent water absorbance (right axis,
black line) using the model described on the
previous slide Water content assumed to be 1
(wt).
31
Impact Expectations Curtain Brightness
The radiance for the ejecta cloud only (derived
be subtracting off the spectra from the lunar
surface) for several times after Centaur impact.
32
Impact Expectations OH- Production
Estimated OH- production and emission line
strengths. Using the water vapor profile in
Slide 4 the total production of OH- was estimated
using a production time constant of 82,000 sec
and a solar flux at 308 nm of 1e20 photons m-2
sec-1 mm-1 str-1. The OH- emission line strength
was estimated using a g-factor (at 308 nm) of
5e-4 photons sec-1.
33
Impact Expectations Side View
Impact Observations Side View
The ejecta cloud will more-or-less look like an
expanding conical section (an upside-down
lampshade). The figure below (images from a
hypervelocity shot at the NASA AVG) demonstrates
this geometry. This shape should be considered
approximate.
lcross_H2Ocolmn_earthview_400.avi
34
Impact Expectations Side View
(a) Estimated ejecta curtain radius, mass
weighted altitude and total mass. (b) The
estimated projected ejecta cloud area assuming a
uniform distribution across a conic volume (see
diagram inset).
(a)
(b)
tntn1Dt
t3
t2
t1
Area
35
Impact Expectations Side View
r 40 mm
For the Edge/Middle Model the ejecta mass fills a
volume described by two conic sections. The
projected area is estimated along the edges and
in the middle portion of the cloud. The edge
area is estimated using an average projected edge
length (calculated from curtain radius and ejecta
angle). The middle area is estimated from the
difference between conic sections, separated by
the curtain wall thickness (assumed here to be
100 meters).
Edge projected length
t3
t2
t1
Edge Area
tntn1Dt
Edge
Middle Area
Middle
36
Impact Expectations Earth Incidence
The Incident Flux at Earth from the ejecta cloud
was estimated using the Area Average and
Edge/Middle models presented on the previous
slides (r40 mm). (a) The Incidence at Earth
using the radiance estimates and ejecta cloud
projected area from the Area Average model. (b)
The Incidence at Earth using the radiance
estimates and ejecta cloud projected area from
the Edge/Middle Average model. Incidence is only
shown for the cloud edge.
37
LCROSS Overview
Backup Slides
38
LCROSS Science Objectives / Measurement Trace
39
Impact Expectations Side View
Estimated ejecta cloud optical depth (assuming a
100 mm spherical particle and 1 wt water ice)
for the Area Average model and the Edge/Middle
model (see diagram below)
r 100 mm
40
In Flight Calibrations
  • Lunar Swing-by
  • For 3 and 4 month cruise, at L5 days payload
    observation deck will be pointed at the impact
    target region of the Moon (South Pole) (2500 km)
  • For 3.5 month cruise, at L5 days payload
    observation deck will be pointed at the Lunar
    North Pole (altitude of 4000 km)
  • At an altitude of 2500 km, visible camera
    resolution 500 meters, spectrometer footprints
    100 km
  • All instruments will be operated in all states
    (wavelength resolution, gain, etc.)
  • Space / Moon / Earth Looks
  • At least 3 attempts prior to impact to monitor
    for instrument trends (degradation /
    contamination)
  • Observations will provide instrument
  • Health
  • Performance
  • Alignment
  • Contamination (water)

41
In Flight Calibrations Lunar Swing-by
42
In Flight Calibrations Lunar Swing-by
Oct28 Trajectory at PerisleneView Looking down
toward sub-satellite point from orbit altitude
Approximate VisCam FOV
Approximate NRSpec FOV
Flight Direction
1
4
2
3
Mare Crisium
Swingby-VIS-v2-HighRes-2min.mov
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