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Lunar Atmosphere and Dust Environment Explorer (LADEE) Mission--a Report Tom Morgan LADEE Program Scientist NASA HQ. Lunar Atmosphere and Dust Environment Explorer (LADEE) Mission--a Report I. Background II. SDT III. Project Snapshot IV. Synergies with Artemis. Background. - PowerPoint PPT PresentationTRANSCRIPT
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Lunar Atmosphere and Dust Environment Explorer
(LADEE)Mission--a Report
Tom MorganLADEE Program Scientist
NASA HQ
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Lunar Atmosphere and Dust Environment Explorer
(LADEE)Mission--a Report
I. BackgroundII. SDT
III. Project SnapshotIV. Synergies with Artemis
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Background
The top eleven science goals identified in the National Research Council’s report, “Scientific Context for the Exploration of the Moon” include:– (a) determine the global density, composition, and time variability of the
fragile lunar atmosphere before it is perturbed by further human activity, and
– (b) determine the size, charge, and spatial distribution of electrostatically transported dust grains and assess their likely effects on lunar exploration and lunar-based astronomy.
The LADEE Mission was designed to address these objectives
Identify a prioritized set of scientific goals that can be addressed in the near term (~2006-2018) by robotic lunar missions…
What What We Know Is There Looks Like
From Potter and Morgan (1998) observations of the Na exosphere using a coronagraph--can be fit with a temperature of 1280 K, falling off with a cos3 function of latitude.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Model of the expected global distribution of Ar-40 at 30 km and 50 km [provided by D. Hodges]. Gas densities peak at the sunrise terminator, where desorption is greatest. The gas densities are sizeable and detectable (> 4000/cc at 50 km).
What What We Know Is There Looks Like-II
Based on what we know is there:• Assaying the lunar exosphere requires that we access a large volume of the space above the Lunar surface;•In general, the closer you go to the surface, the better;•The distribution of each species is different, and the distribution is variable.
What What We Know Is There Looks Like--Dust
There is additional evidence for dust from the Apollo 17 ALSEP LEAM experiment, and from Clementine Observations.
Surveyor 6
Horizon Glow at Twilight.--most likely explanation is forward scattering of Sunlight by dust
Cernan sketched observations of streamers in the Sunrise horizon as the CSM approached local sunrise.
Based on what data we have on dust:• Most of the dust is close to the surface;•Most of the dust is small.
LADEE Science Definition Team• Began recruiting a small LADEE Science Definition Team
early in February.• Very focused direction--composition of atmosphere, and
Characterization of dust.• Constrained to 3 instruments and a target payload mass of 20
Kg--encouraged to think “off the shelf” in response to aggressive launch date.
• Work with ARC orbiter design for a low orbit (50 km), and a minimum 3 month prime mission.
• Mid-term report expected no later than April 21, with Final Report by May 21---both met.
• SDT could work with project--we did.• RFI assessment completed after the SDT report was
submitted by HQ/GSFC/ARC team.
Science Definition TeamLaurie Leshin, NASA Goddard Space Flight Center (Chair)William Farrell, NASA Goddard Space Flight Center (Vice Chair)Dana Crider, Catholic University of AmericaRick Elphic, NASA Ames Research CenterPaul Feldman, Johns Hopkins UniversityDick Hodges, University of Texas at Dallas (Emeritus)Mihaly Horanyi, University of ColoradoWayne Kasprazak, NASA Goddard Space Flight Center Richard Vondrak, NASA Goddard Space Flight Center
Ex Officio MembersSteve McClard, NASA Marshall Space Flight Center, LADEE Mission ManagerButler Hine, NASA Ames Research Center, LADEE Project ManagerWill Marshall, NASA Ames Research Center, LADEE Flight DynamicsThomas Morgan, NASA HQ, HQ LiaisonSarah Noble, NASA HQ, HQ LiaisonKelly Snook, NASA HQ, HQ Liaison
With help from IMS focus group (R. Elphic, lead): M. Collier, E. Sittler, J. Keller NASA/GSFC
LADEE Atmosphere Findings - Species that make up exosphere 1) prevalent at 50 km altitude 2) maximize at sunrise terminator3) peak densities at equator
- Species can be categorized by their sources, including solar wind, regolith and radiogenic
- Ar, He, H/H2, OH, CH4, CO, CO2, Na, K, Si, Al, Fe all of interest
- No one instrument/technique can obtain all species of interest
- Mission lifetime of a year is ideal, but new, interesting science can be done in 3 mo.
- A NMS will likely detect Ar, He, H2 but will have great difficulty with trace species requiring a supporting instrument
Model results from R. Hodges for LADEE SDT
LADEE Dust Findings- Two dust components: 1) Dust of Lunar Origin (DoLO)2) Interplanetary Dust (IDP)
- DoLO peaks near terminator with 50 km densities at ~10-4/cc, IDP detected at all longitudes
- Distinct Targets-of-Opportunity for improved dust observations:
• Known meteor shower/comet tails• Magnetotail/plasma sheet crossings• Solar Storms
- DoLO single impacts very difficult to detect since grains are submicron and slow
- Remote sensing UV/VIS instrument will provide critical complementary data to in situ observations
Clementine ‘94
Stubbs et al 2006
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LADEE Dust Recommendations
- Any in situ dust detector needs sensitivity to submicron levels to detect DoLO
- Take full advantage of periods when external environment is being driven extra hard, like during solar storms, plasma sheets crossings, meteor showers
- Because of difficulty in DoLO detection, recommend the use of supporting remote sensing UV/VIS sensor
- At least one lunation to get through tail, likely see a meteor shower and solar storm
M. Horanyi for SDT
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LADEE Spacecraft/Trajectory Findings- Most active science location: Periseline
at < 50 km over sunrise terminator
- Retrograde orbit (keep instruments in ram but out of sunshine)
- Equatorial orbit preferred over polar orbit: Densest portion of exosphere, don’t expect emitted polar water from cold traps. LADEE can contribute to search for water by “following the OH” and examining the terminator desorption processes
- Ideal orbit: Circular, retrograde, low inclination
- Spacecraft is “dirty” and will have the potential to contaminate instruments via outgassing, thruster firings, and EMI
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SDT Critical/Strong RecommendationsRecommentations Source of Recommendation
1.1 LADEE Science Objective 1: “Determine the composition of the lunar exosphere and investigate the processes that control its distribution and variability, including sources, sinks, and surface interactions.
Consistent with SCEM Goal 8a. Goes beyond a “when and where” survey to examine “why” species are there.
1.3 While a complete and instantaneous composition of a sample environment may not be obtained, a sampling of species in each of the primary sources (solar wind, regolith, and radiogenic) is desired.
Consistent with Objective 1
1.4 Fly a set of instruments that reliably provides the largest possible coverage of species detection.
To obtain a set of species in each source category, LADEE will need a number of complementary instruments (a set).
1.5 The set of instruments should fly for no less than one lunation to ensure LADEE passes through the magnetotail.
Varying plasma environment will impact sputtering. Over one lunation there is also the likelihood of passing through a meteor stream and some likelihood of being present during a solar storm.
2.1 LADEE Science Objective 2: “Characterize the lunar exospheric dust environment and measure any spatial and temporal variability and impacts on the lunar atmosphere.”
Consistent with SCEM Goal 8a.
2.4 Use of both in situ and UV remote sensing techniques to obtain a complementary and consistent dust detection data set.
I t will be a challenge for in situ dust detection to sense small lofted dust. UV provides a reasonable supporting capability.
2.5 Dust measurements should occur over at least one lunation. Driven by the need to have a passage through the magnetotail/plasmasheet where surface potentials are large and negative (drive lofted dust to higher altitudes).
3.1 The SDT recommends that the orbit be retrograde, and as close to circular, with as low an altitude and as low an inclination as possible (but no higher than 50 km and inclination 180deg +/- 20), consistent with delivering a payload mass of at least 20 kg.
Retrograde orbit for instrument protection (ram out of sunlight during lunar-sunrise terminator passes), equatorial orbit passes through greatest gas concentration, and 20 kg allows NMS, dust, and supporting instrument measurements.
3.2 The orbit target is a box of +/- 5 km centered at 45 km altitude or lower over the lunar-sunrise terminator.
Lunar atmosphere has largest concentration at this terminator.
3.4 Project provides a systemic approach to spacecraft environmental cleanliness, including early development of plans to optimize outgassing, thruster firings, and EMI .
Spacecraft is “dirty” and emissions could set the background thresholds for gas and dust detection.
4.1 The SDT recommends creation of a strong science team, both in instrument selection and in an active participating science community.
LADEE should not just buy instruments; needs science expertise to achieve the objectives.
4.2 A lunar observation ground campaign to occur concurrent with the LADEE mission should be supported by the mission.
To support and complement the LADEE observation set.
Lunar Gas Exosphere
Lunar Dust Exosphere
Spacecraft/Trajectory Recommendations
Programmatic Recommendations
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LADEE Mission Timeline
• 2/4/2008 - LADEE Announced• 4/7/2008 - LADEE Authorization Letter from AA/SMD• 3/24/2008 - LADEE Instrument RFI Released• 4/1/2008 - LADEE Spacecraft Technical Interchange Meeting• 4/8/2008 - PPBE Submit to SMD• 4/21/2008 - Launch Accommodation Study Completed• 5/21/2008 - Science Definition Team Final Report• 8/12/2008 - Initial Payload Concept Studies Completed• 8/19/2008 - SMD Guidance on LLCD Payload• 8/20/2008 - Flight Planning Board Approval for Minotaur V• 8/24/2008 - Initial Payload Accommodation Study Completed• 10/1/2008 - Project Mission Concept Study Guidance Received• 10/21/2008 - Mission Concept Study Kick-Off• 12/8/2008 - Mission Concept Review Scheduled
DATE ACTION
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Programmatics-ILunar Atmosphere & Dust Environment Explorer (LADEE)
Mission ObjectivesDetermine the composition of the lunar atmosphere and investigate the processes
that control its distribution and variability, including sources, sinks, and surface interactions
Characterize the lunar exospheric dust environment and measure any spatial and temporal variability and impacts on the lunar atmosphere
Demonstrate LLCDCreate a low cost reusable spacecraft architecture that can meet the needs of
certain Planetary Science MissionsDemonstrate the use of Minotaur V as a launch vehicle for planetary mission
Key parametersLaunch: 2011Science Data Acquisition: 3 months (following short check out period) after which
we demonstrate Laser communicationSpacecraft
Type: Small Orbiter - Category 3, Class DProvider: ARC provided small sat (partnered with GSFC)Cost: $100M LADEE with 3 science instruments; $46M LV $54M LLCD
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Programmatics-IIInstruments
Science Instruments: NMS (directed to GSFC), UV/VIS (directed to ARC), and Dust Detector (competed through the SALMON AO (on the street)
Technology Payload: Lunar Laser Communications Demonstration (LLCD) instrument ( LLCD), funded by SOMD (managed by GSFC).
Science Team The Project Scientist will provide science team coordination functionsScience decisions arrived at by consensus between the Instrument Pis through
Project Science Group (PSW)Conflicts that can’t be resolved internally will be elevated to the LADEE
Program ScientistEach directed instrument will each contribute three members to the initial
science teamThe Dust team element of the Science Team will be determined through the AO
competitionA Participating Scientist call will be offered through the ROSES
Launch VehicleMinotaur V (out of Wallops)--still requires DoD approval
LADEE Science RequirementsIn order to accomplish the science objectives, the LADEE mission shall meet the
following baseline science requirements:
o Measure spatial and temporal variations of Ar, He, Na, and K over time scales from several (3) lunar orbits to one lunation.
o Detect or obtain new lower limits for other species for which observations have been made. These include the following elements or compounds and the current limit* (part/cm3); CH4(1x104), S(150), O(1x103), Si(48), Kr(2x104), Xe(3x103), Fe(3.8x102), Al(55), Ti (1), Mg(6x103), OH(1x106), and H2O(100).
o Search for other species (beyond those listed in the previous two bullets) or positive ambient ions of these species and other atoms or compounds in the 2-150 Da mass range.
o Detect or set upper limits as small as 10-4 dust particles / cm 3from 1.5 to 50 km altitude for particles as small as 100 nm via occultation measurements.
o Detect or set upper limits on the dust population at 50 km.*Limits measured against Table 1.1, S. A. Stern, Reviews of Geophysics, 37, 453, 1999. (Stern contains no limit for H20)
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Lunar Atmosphere and Dust Atmospheric Explorer Neutral Mass Spectrometer
The Lunar Atmosphere and Dust Atmospheric Explorer (LADEE) Neutral Mass Spectrometer (NMS) will (with the Ultraviolet Spectrometer-next chart) determine the composition of the lunar atmosphere from an orbit of 50 km above the surface and for a period of one lunation.
Features:• NMS is a high sensitivity quadrupole mass spectrometer with a mass range to 150 Dalton and unit mass resolution. • For lunar orbits of 50 km or lower NGIMS can measure the abundance and variability of helium, argon, methane and other species either released from the deep lunar interior or from the surface of the moon. • The NM is designed to produce a substantial improvement in sensitivity and spatial coverage from Apollo era instruments. It will characterize this environment before it is irreversibly changed by human activity.
Team: Instrument PI: Dr. Paul Mahaffy/GSFC Instrument Manager: Jim Kellogg/GSFC
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Lunar Atmosphere and Dust Atmospheric Explorer Neutral Mass Spectrometer
The Lunar Atmosphere and Dust Atmospheric Explorer (LADEE) Neutral Mass Spectrometer (NMS) will (with the Ultraviolet Spectrometer-next chart) determine the composition of the lunar atmosphere from an orbit of 50 km above the surface and for a period of one lunation.
Features:• NMS is a high sensitivity quadrupole mass spectrometer with a mass range to 150 Dalton and unit mass resolution. • For lunar orbits of 50 km or lower NGIMS can measure the abundance and variability of helium, argon, methane and other species either released from the deep lunar interior or from the surface of the moon. • The NM is designed to produce a substantial improvement in sensitivity and spatial coverage from Apollo era instruments. It will characterize this environment before it is irreversibly changed by human activity.
Team: Instrument PI: Dr. Paul Mahaffy/GSFC Instrument Manager: Jim Kellogg/GSFC
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LADEE Atmosphere UV/Vis Measurements
Species
Minimum Detectable
# per cc
OH 15040Al 200Ca 15.04
Ca+ 80Fe(1) 1216Fe(2) 624
K 2.16Li 0.232Na 6.88Si 128Ti 5.44Ba 0.336Mg 45600
H2O+ 784H2O+ 568
O 2640
Measured Atmospheric Species (At SNR=5)
S/C
Atmosphere or Dust
Limb FOVScatter + Emission
Solar Occultation FOV
Dust Occultation Detection Limit
0.00001
0.0001
0.001
0.01
0.1
1
0.23 0.43 0.63
Wavelength (mm)
Optical Depth = 10-3
r=1000 nmr=100 nmr=10 nmRequired R (SNR=5), Nscan=1Required R (SNR=5), Nscan=100
- Target A: For known species (Na, K; use them as markers for variability
- Target B: For expected species, reduce known limit or make the discovery detection
- Sample species in each of three source categories
- Monitor dust component
- Measure for at least one lunation
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Lunar Laser Communications Demonstration
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Lunar Laser Communications Demonstration
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Spacecraft Bus
•Payload Module
•Bus Module
•Extension Module
•Propulsion Module
LADEE Bus Derived from ARC Common Modular Bus Design:
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Baseline LADEE Payload Locations
NMS
DD
LLCD
UVS
NMS
DD
LLCD
UVS
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Science Data Acquisition Phase
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Lunar Science Orbit: 50Km Retrograde
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Launch Vehicle Target: Minotaur V
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Artemis Mission Concept
Probe instruments:ESA: ElectroStatic Analyzer(coIs: Carlson and McFadden)SST: Solid State Telescopes (coI: Larson)FGM: FluxGate Magnetometer(coIs: Glassmeier, Auster & Baumjohann)SCM: SearchCoil Magnetometer (coI: Roux)EFI: Electric Field Instrument (coI: Bonnell)
SST
ESA
EFIa
EFIs
FGM
SCM
Tspin=3s
D29
25-1
0 @
CC
AS Lunar Wake
Formation/Evolution
Diffusive Particle
Acceleration
Shock tangent
Foreshock waves
Turbulent wake?
Last closed field lineGeotail
THEMISMoon
P1P2
P1 P2Solar Wind
X
Magnetotail
Combined GoalsHeliophysics from the MoonEM Environment of the MoonDust Levitation in E-fieldComposition of the ExosphereDistribution of the ExosphereEM sounding of Interior