NASA's Lunar Atmosphere and Dust Environment Explorer: Little Mission, Big Science
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LIVE INTERACTIVE LEARNING @ YOUR DESKTOP NASA's Lunar Atmosphere and Dust Environment Explorer: Little Mission, Big Science Presented by: Dr. Rick Elphic and Brian Day May 31, 2011 Lunar Atmosphere and Dust Environment Explorer: Little Mission, Big Science May 31, 2011 NSTA Webinar Rick Elphic, LADEE Project Scientist NASA Ames Research Center Moffett Field, California Outline of Talk 1. Science Background for LADEE 2. LADEE Payload: 3 science instruments, 1 tech demo 3. LADEE Spacecraft 4. LADEE Launch Vehicle 5. LADEE Mission Profile 6. Schedule & Cost LADEE: Big Science 3 Science Background LADEE: Science Focus Lunar Exosphere: A nearby example of a common type of atmosphere, the Surface Boundary Exosphere. Dust: Does evidence point to electrostatic lofting? In 2008, the door opened to investigate these questions: NASA Hq directed Ames Research Center to do the LADEE mission. LADEE: Big Science 5 LADEE Science Background • 2003 NRC Decadal Survey: “New Frontiers in the Solar System: An Integrated Exploration Strategy” • LEAG Roadmap Objective Sci-A-3: Characterize the environment and processes …in the lunar exosphere • National Research Council (NRC) report, “Scientific Context for the Exploration of the Moon” (SCEM) • 2011 NRC Decadal Survey: “Vision and Voyages for Planetary Science in the Decade 2013-2022” – Execute LADEE mission LADEE: Big Science 6 Exospheres and Dust Surface Boundary Exospheres (SBEs) may be the most common type of atmosphere in the solar system… Large Asteroids & KBOs Itokawa Moon Europa & Evidence of dust motion on other Icy asteroids and the Moon.... satellites Io Rhea LADEE CDR ITAR RESTRICTED MATERIAL WARNING Eros MayLADEE: 17-20, Big2011 Science 7 7 Lunar Exosphere – Measurements Surface measurements: Ar and He Earth-based measurements: Na and K 40 LACE Ar Measurements We know that Ar, , Na and K exist in the exosphere. LADEE CDR ITAR RESTRICTED MATERIAL WARNING MayLADEE: 17-20, Big2011 Science 8 8 SELENE/Kaguya Observations of Na • UPI-TVIS instrument • Viewed Na column away from Moon • Distribution consistent with hot source (2000 – 6000 K) LADEE: Big Science 9 9 SELENE/Kaguya Observations of Na • UPI-TVIS instrument • Viewed Na column away from Moon • Distribution consistent with hot source (2000 – 6000 K) • Density varies over 3- month timescale • Density appears to decrease between 1st quarter and 3rd quarter LADEE: Big Science 10 10 The Moon has a Sodium Tail! • The Moon’s Na exosphere doesn’t stay put – it blows away! • At New Moon, the Na atoms going antisunward are gravity-focused by Earth. • All-sky images from Earth reveal this anti- solar tail. LADEE: Big Science 11 11 The Moon has a Sodium Tail! • The Moon’s Na exosphere doesn’t stay put – it blows away! • At New Moon, the Na atoms going antisunward are Off-band subtracted gravity-focused by Earth. • All-sky images from Earth reveal this anti- solar tail. LADEE: Big Science 12 12 Lunar Exosphere – Solar Wind Input (Wieser et al, 2009) Chandrayaan Neutral Particles: >1 eV neutral hydrogen is lost. LADEE: Big Science 13 13 “Disappearing” Surficial H2O and OH • Chandrayaan-1 M3, EPOXI and Cassini VIMS 3-μm observations. • Presence of H2O and OH in/on surface grains: o Signature deepest at high latitudes and off-noon local times. o Where do OH, H2O go? Into exosphere? Polar cold traps? Pieters et al Science 2009 Clark et al Science 2009 LADEE: Big Science LADEE ITAR RESTRICTED MATERIAL 14 LCROSS Impact Results Water Vapor and Water Ice in Model Fit: 7.4% ± 5% by mass Add other species: CH4, CO2, SO2 LADEE: Big Science LADEE ITAR RESTRICTED MATERIAL 15 15 Lunar Dust: Electrostatic Levitation? Lunar Ejecta and Meteorites experiment (LEAM) Terminators Berg et al., 1976 • Apollo surface experiment LEAM detected dust activity correlated with the lunar terminators LADEE: Big Science 16 Lunar Dust: Electrostatic Levitation? • Surveyor 7 images of lunar horizon glow (“LHG”) • Prevailing theory: <10 μm dust, ~150m away, ~1m high on sunset horizon LADEE: Big Science LADEE ITAR RESTRICTED MATERIAL 17 Lunar Dust – in Orbit? Gene Cernan sketches from Apollo McCoy and Criswell, 1974 Command Module Apollo CM Trajectory Dust? • Eyewitness accounts of “streamers” from Apollo command module • Too bright to be meteoritic ejecta • Exosphere and/or high altitude (50 km) dust is one possibility • Key goal if LADEE is to help resolve this open question LADEE: Big Science LADEE ITAR RESTRICTED MATERIAL 18 18 LADEE Project Level Science Objectives • LADEE Objective 1: Determine the composition of the lunar atmosphere and investigate the processes that control its distribution and variability, including sources, sinks, and surface interactions. • LADEE Objective 2: Characterize the lunar exospheric dust environment and measure any spatial and temporal variability and impacts on the lunar atmosphere. JulyLADEE: 20 Big – Science 23, 2010 LADEE ITAR RESTRICTED MATERIAL 19 19 Let’s pause for questions from the audience LADEE Payload LADEE Payload: 3 science, 1 tech demo Neutral Mass Spectrometer (NMS) UV-Vis Spectrometer (UVS) Dust and exosphere MSL/SAM Heritage SMD - directed instrument LCROSS heritage measurements SMD - directed instrument In situ measurement A. Colaprete of exospheric NASA ARC species P. Mahaffy NASA GSFC 150 Dalton range/unit mass resolution Lunar Dust EXperiment (LDEX) Lunar Laser Com Demo (LLCD) HEOS 2, Galileo, Ulysses and Cassini Heritage Technology demonstration SMD - Competed instrument High Data Rate SOMD - directed instrument M. Horányi Optical Comm LASP D. Boroson MIT-LL 51-622 Mbps LADEE: Big Science 22 LADEE Neutral Mass Spectrometer Measurement Concept: • High-sensitivity quadrupole mass spectrometer, mass range 1 - 150 Dalton and unit mass resolution. • At 50-km or lower can detect helium, argon and other species. • Ultra high vacuum (UHV) materials and processing used in the fabrication of NMS yield a substantial improvement over background instrument noise from Apollo era instruments, corresponding increase in sensitivity of the measurement. • The sensitivity is necessary to adequately measure the low density atmosphere of the moon. NMS Team: Performance Data: • Instrument PI: Dr. Paul Mahaffy/GSFC • Closed Source species: He, Ar, non-reactive neutrals • Instrument Manager: Dr. Todd King/GSFC • Open Source species: neutrals and ions • Instrument SE: Jim Kellog/GSFC • Mass Range: 2 - 150 Da • Mass Resolution: unit mass resolution over entire range • Sensitivity: 10-2 (counts per second) / (particles per cc) Participating Organizations: • Mass: 11.3 kg • NASA/GSFC • Volume: 23,940 cm3 • U. Michigan/Space Physics Research Lab • Envelope: 43.2 cm x 24.5 cm x 37.0 cm • Power: 34.4 W average • Battel Engineering • CDH interface: 422 differential • AMU Engineering • Data Rate: 3.5 kbs • Nolan Engineering • Data Volume: 8.5e6 bits per orbit (assuming 40% duty cycle over a 113 min circular orbit) LADEE: Big Science 23 Mass spectrum from CoNTour NMS LADEE: Big Science 24 UV/Vis Spectrometer (UVS) Measurement Concept: • UVS includes UV-VIS Spectrometer, telescope, solar diffuser, & bifurcated optical fiber • UVS observations consists of limb and occultation measurements • Limb observations measure the lunar atmosphere, & also measure limb dust by measuring back- or forward-scattered sunlight • Solar occultation observations measure lunar atmospheric dust extinction from 0 to 50 km Team: Performance Data: • PI/PM: Dr. Tony Colaprete / ARC • In Limb mode measures atmospheric species • Instrument SEs: Leonid Osetinsky / ARC including: K, Na, Al, Si, Ca, Li, OH, H2O and Ryan Vaughan / ARC • By combining long integration times, UVS measures each specie to < current upper limits • In limb mode measures dust (via scatter) at Participating Organizations: concentrations as low as 10-4 per cc for r=100 nm • NASA/ARC size particles. • Aurora Design & Technology • In occultation mode measures dust (via • Visioneering, LLC extinction) at concentrations as low as 10-4 per cc for r=100 nm size particles down 300 meters alt. • 3.98 kg LADEE: Big Science • 14 W (average operation) 25 July 20 – 23, 2010 Anticipated SNR Exospheric Species LADEE: Big Science 26 Lunar Dust Experiment (LDEX) Measurement Concept: • LDEX is an impact ionization dust detector • Measures the mass of individual dust grains with m ≥ 1.7x10-16 kg (radius rg ≥ 0.3 micron) for impact speeds ≈ 1.7km/s • Also measures the collective current due to grains below the threshold for individual detection, enabling the search for dust grains with rg ≈ 0.1 micron over the terminators Team: Performance Data/Key Science PI: Mihaly Horanyi PM: Mark Lankton • Characterizes the dust exosphere by mapping size and spatial distribution of IS: Zoltan Sternovsky dust grains SE: David Gathright • Measures relative contribution of dust Participating Organization: sources: interplanetary vs. lunar origin. Laboratory for Atmospheric and Space • Mass: 3.45kg (with reserves) Physics, University of Colorado • Power: 6.11W peak, 5W ops (with reserves) • Data: 1kb/s LADEE: Big Science Payload: 27 27 How LDEX works… ions electrons LADEE: Big Science 28 LDEX Dust Accelerator data LADEE: Big Science 29 LLCD Technology Demo Objectives/Features: • Demonstrate laser communication between the Earth and the LADEE spacecraft in lunar orbit. NASA’s first step in developing high performance laser communications systems for future operational missions. • Demonstrate major functions – High bandwidth space to ground link using an optical terminal – Robust pointing, acquisition, tracking LLCD has three primary parts: – Duplex