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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 functions

Science 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 Scientist

Each directed instrument will each contribute three members to the initial science team

The Dust team element of the Science Team will be determined through the AO competition

A Participating Scientist call will be offered through the ROSES

Launch Vehicle

Minotaur 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 FOV

Scatter + 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