Colaprete LCROSS overview

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Information about Colaprete LCROSS overview
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Published on November 14, 2007

Author: Christo

Source: authorstream.com

Slide1:  Anthony Colaprete and the LCROSS Team Slide2:  LCROSS Mission Selection LCROSS mission was selected on 4/10/06, via an ESMD two-step AO Step 1: Proposal generation (Pre-Phase A formulation phase) Step 2: Down-select of field of (19) proposals to (4) (Phase A formulation phase) Step 3: Selection of LCROSS proposal (Phase B entrance) Slide3:  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 2000[kg] (4410[lb]) Centaur into a permanently-shadowed crater at 2.5[km/s] (1.56 [miles/s]) ~200 metric tons (220 tons) minimum of regolith will be excavated, leaving a crater the size of ~1/3 of a football field, ~15 feet 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] (1,543[lb]) 'impactor' as well Lunar-orbital and Earth-based assets will also be able to study both clouds, (which may include LRO, Chandrayaan-1, HST, etc) LCROSS Mission Overview Slide4:  A fast, capable team: ARC provides the overall project management, systems engineering, risk management, and SMA for the mission Northrop-Grumman provides the S/C and S/C integration for this mission as well as launch systems integration support ARC provides the Science, Payloads, and Mission Ops for this mission ARC, JPL, and GSFC provides the Navigation and Mission Design role JPL is providing DSN services KSC/LM is providing Launch Vehicle services JHU-APL is providing avionics environmental testing LCROSS Project Team Slide5:  LCROSS Science Team Tony Colaprete (ARC) Geoff Briggs (ARC) Kim Ennico (ARC) Diane Wooden (ARC) Jennifer Heldmann (SETI) Tony Ricco (Stanford) Luke Sollitt (NGST) Andy Christensen (NGST) Erik Asphaug (UCSC) Don Korycansky (UCSC) Peter Schultz (Brown) Principal Investigator Deputy Principal Investigator Payload Scientist Observations/Analysis Observation Coordinator NIR Spectrometers Imaging systems Science Requirements Impact Processes Impact Processes Impact Processes Slide6:  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 The LCROSS mission rational: The nature of lunar polar hydrogen is one of the most important drivers to the long term 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 Mission Measurement Objectives Clementine Mosaic - South Pole Neutron Map - South Pole (Elphic et al.) Slide7:  Pre-Launch Launch Transfer VIF Ops Pad Ops LV Ascent Park Orbit Coast LRO Inject/Sep Centaur Venting & Re-Target Centaur Handover To LCROSS Checkout TCM-1 TCM-2 TCM-3 Swing by Calibration [TCM-4] Day -1 Day 0 Day 2 Day 1 Day 3 Day 4 Day 5 Day 6 Day 7 Cruise Final Targeting Day 15 Day 36 Day 57 Day 69 Impact and Data Collection Final Targeting Burn EDUS Separation Braking Burn Data Collection EDUS Impact S-S/C Impact Day 86 Day 85 Day 64 [TCM-6] [TCM-7] TCM-9 [TCM-5] TCM-8 Day 76 TCM-11 Timp– 8hrs Timp– 7hrs Timp– 6.5hrs Timp– 2hrs T = 0 Timp+ 10min TCM-10 Mission Timeline Slide8:  ( Click green button to start QuickTime movie ) LCROSS Mission Animation Slide9:  The Atlas Centaur Impact: Mass: ~2000 kg Velocity: 2.5 km/sec Angle: ~75 degrees Minimize false positives by controlling EDUS contamination Total H/O bearing materials (e.g. LOX, H2, H2O in batteries) kept below reported and kept below 100 kg Minimize false negatives by combining multiple detection methods Crater Diameter, Depth and Excavated Water (Assumes a 10 cm desiccated Layer with uniform water mixing below) …using 6.5 Billion Joules Prospecting for Water Slide10:  CBEIM Crater Size The Current Best Estimate Impact Model (CBEIM) The CBIEM summarizes the results of numerous impact models / assessments. Used as the base to drive mission design and instrument selection. Efforts continue to refine the model with an update due December, 2006. Slide11:  Montecarlo study of ejecta mass: Simulation varied the crater radius (Rcrat), velocity function exponent (a), total mas (Me), and ejecta flight angle (q). (See LCROSS technical note “LCROSS ejecta dynamics–Monte Carlo model (09/16/06)“ for details) Montecarlo Study of Ejecta Mass Average Median Slide12:  Average Ejecta Curtain Characteristics – 1% water content CBEIM and Sensitivity Studies Slide13:  Stages of the Impact Process Ejecta Curtain Simulation using the Ames Vertical Gun Range Peter Schultz Slide14:  Impact Flash and Vapor Cloud Visible Component: Compaction / Intergrain Strain t~0.1 sec F~0.001-1 mW m-2 (r=1000 km) NIR Component: Blackbody Emission of Vapor Cloud t~1 sec F~0.01-10 mW m-2 (r=1000 km) Total energy sensitive to target properties such as material strength, density and water content. Shape of the curve reflects the penetration depth, changes in material competence A variety of visible and NIR spectral emissions relate to composition of target material and the fraction of the impactor which vaporizes Lunar Flash AVGR Flash Flash Brightness vs Time Stages of the Impact Process Slide15:  Ejecta Curtain Evolution After the flash, target material is ejected outward on ballistic trajectories. Visible Component: Curtain illuminated by sunlight Spectral brightness dependant on particle density, size, composition, shape Excitation / Florescence from species such as OH- and H2O+ NIR Component: Curtain illuminated by sunlight Spectral brightness dependant on particle density, composition, size, shape Mid-IR Component Curtain thermal emission Evolution sensitive to initial ejecta temperature (~100 K), particle size, volatile composition (water) and solar exposure Grains with radii <100 mm will warm within ~1-100 seconds to ~250 K after solar exposure. Spectral brightness dependant on particle density, composition, size, shape Stages of the Impact Process Slide16:  Curtain Clearing / Crater Exposure After ~5 minutes the bulk of the ejecta “settles” exposing the fresh crater Mid-IR Component Remnant thermal emission from the crater (l=6-15 mm) At 5 minutes post impact the crater temperature will be ~200 K, against a ~100 K background Crater temperature sensitive to water content Determination of crater size Temperature of Crater Floor After Impact Stages of the Impact Process Slide17:  LCROSS Measurement Plan Flash Photometry Total brightness in visible and NIR wavelengths Visible Spectroscopy Visible emission (e.g., OH-, H2O+) Surface and ejecta curtain reflectance/absorption NIR Spectroscopy Surface and ejecta curtain reflectance/absorption NIR Imaging Surface and ejecta curtain reflectance Band-depth maps (l=1.4 mm) Middle IR Imaging Surface and ejecta curtain temperatures Band-depth maps (l=12 mm) Visible Imaging Surface and ejecta curtain reflectance Slide18:  Measurement / Technique Trace Direct / Strong = Very direct measure with little modeling / assumption; highly sensitive Indirect / Strong = Indirect measure with the goal removed by several steps; highly sensitive Indirect / Weak = Indirect measure with the goal removed by several steps; moderately sensitive Slide19:  LCROSS Orbit & Impact Geometry Nominal Impact Conditions: Target impact site: Shackleton Crater (-89.5 lat; 0 lon) Incident impact angle: ~75 deg Impact velocity: 2.5 km/sec Slide20:  Basic S/C Concept Hybrid propulsive control authority: 5[lbf] thrusters for large delta-V 1[lbf] thrusters for high precision control authority for attitude control No deployments or mechanisms except separation bands Straight load path LRO accommodation with high structural margins ESPA ring used as the primary spacecraft structure, similar to the AFRL DSX mission. TDRSS tank supported on a simple cone on the upper ESPA ring interface Propulsion booms and equipment panels attach to Secondary Payload Interfaces D1666VS PAF & Spacer B1194VS PAF & Spacer Centaur ESPA Ring Slide21:  Space Vehicle Overview Star tracker PL Optical Bench Omni antenna (2) - 4 pi steradian coverage Adjustable MGA (2) +/- 20 deg FOV +/- 45 deg adjustability pre-launch Solar array Propellant tank - Mounting skirt PL support structure Thruster mounting brackets (4) - Two 22N and eight 5N total ESPA ring - Six attachment ports LRO derivative spacecraft avionics distributed on 5 equipment panels C&DH, PSE, PDE, STA, IRU, Transponder, RF components Slide22:  9 Instruments: 1 Visible Context Camera: 4 color, 6 degree FOV, <0.5 km resolution at T-10 min to S-S/C impact 2 NIR Cameras 1.4 mm water ice band depth maps 1 km resolution at T-10 min 2 mid-IR Cameras 7 and 12.3 mm < 0.5 km resolution 1 Visible Spectrometer 0.25 to 0.8 mm, ~0.002 mm resolution 2 NIR Spectrometers 1.35 to 2.45 mm, 0.012 mm resolution 1 Total Visible Luminance Photometer Broadband from 0.6 – 1.2 mm, sample rate >1000 Hz, < nW NEP @ 1000 Hz Payload Overview Slide23:  Instrument sensitivity calculated using CBEIM, scattering calculations, and instrument performance models LCROSS S-S/C Utilizes backscattered solar light to make water absorption measurements (Differential Absorption Spectroscopy) Ejecta Curtain Scattering Assumptions (for NIR): Dominant Particle Radius = 45 mm Particle Density = 2000 kg/m3 Single Scatter Albedo = 0.8 Asymmetry Factor = 0.8 q = 30° Earth-Sun-Moon Geometry 30 °>q>160° Instrument Sensitivity Studies q Backscatter Geometry from an Solar Illuminated Curtain Slide24:  Instrument Sensitivity Studies Time after impact, t = 60 sec N = 1 scan N = 10 scans a) b) NIR Spectrometer Sensitivity to 1% Regolith Water Concentration Slide25:  Instrument Sensitivity Studies Instrument Sensitivity Example – Visible and MIR Cameras Camera Resolutions Each point represents a IR camera image Camera FOVs Maximum Expected EDUS Crater Rim Diameter Slide26:  Potential Supporting Platforms LRO International lunar missions Earth-orbiting Ground based These platforms can provide unique vantage points and capabilities to monitor the impact event for water. LCROSS provides support to these missions in the form of science rationale, impact expectations, observation recommendations, and technical data for observation (e.g., timing, direction for telescope pointing). Working directly with Facility/Instrument leads to plan observations (e.g., HST, SWAS, LRO, Keck). LCROSS Co-I has participated in the observation of SMART-1 to gain experience in observing the moon using large earth based telescope. Information will be provided through a web portal, modeled after the very successful Deep Impact mission. Impact Observations Support LRO HST Keck Slide27:  Impact Observations Support q The opportunity for ground based assets to observe the impact depends on the date and time of impact: Phase of the moon: q >30° from new or full moon Moon position in the night sky: <2 air masses (f>45 ° from horizon) with >2 hours of observing time q Full Moon New Moon f Slide28:  Impact Observations Support Platform / Instrument to Measurement Trace Slide29:  LCROSS Payload Data Plan Receive Level-1 data (uncalibrated) from MOS MOS station to Science station All calibration and analysis performed by Science Team Analysis / Retrieval routines developed prior to impact Will adopt the LRO coordinate system Impact + 3 months: The LCROSS payload data will be calibrated and reduced to physical units A report on the LCROSS payload results will be delivered to LPRP and ESMD Impact + 6 months: The LCROSS Payload data will be appropriately formatted and delivered to the PDS Slide30:  S-S/C Performance Instrument Performance Radiance Predictions Chemistry Predictions Impact Site Selection Project Constraints Trades Inputs / Requirements Mission Goals Impact Predictions The impact model predictions formed the bases for mission design and instrument selection. Mission Design and the Impact Slide31:  The uncertainty to which we know where a place and altitude is on the Moon is a function of both latitude and longitude. Current uncertainties in lunar geodetic maps are: ±3-4 km in the horizontal and ~±0.5 km in the vertical. Newest USGS map (due in January 2007), these errors may be as small as ~±1 km in the horizontal. This error will be reduced by the time of impact: Using LRO data can reduce current uncertainty by a factor of ~2. Impact Site Selection – The Geodetic Map Maximum (uncorrelated) targeting error, assuming unimproved geodetic map, is ±4 - 5 km (3s). Current S-S/C targeting performance estimated to be better than ±1 km (3s). Clementine Mosaic of South Pole Slide32:  The mission baseline is to impact Shackleton Crater Shackleton meets the primary criteria for targeting: Shadowed Large (D>10 km) Apparent association with increased [H] High latitude (Impact Angle >70°) Near side with portion of interior visible to Earth Impact Site - Baseline Shackleton LP Neutron Counts (Maurice et al.) Blue indicates [H] Radar Topography (Margot et al.) Slide33:  Shackleton may not be the best target given secondary considerations, including: Visibility to Earth assets (lat and lon) and Lunar phase (position of terminator) Site surface properties, including regolith depth (age) and surface roughness (effects the total ejecta dynamics and volume) A Target Selection Committee will consider all candidates and weigh their merit against: Project constraints (e.g. targeting accuracy) Project impact (due to departure from baseline) Primary and secondary considerations. Impact Site Selection - Adjustments Slide34:  Impact Site Selection - Process Targeting Committee Workshop Input Project Impact ESMD / LPRP Other Input Project (Baseline) “Top Five” Project (Final) Slide35:  Backup Slides Backup Sides Slide36:  CBEIM Ejecta Curtain Geometry EDUS Separation Selection To maximize S-S/C instrument response, instrument FOV should be filled at peak sunlit ejecta opacity Sunlit ejecta opacity: Maximum sunlit ejecta mass (assuming a 2 km sun-mask) occurs at ~1 min after impact At 1 min after EDUS impact the ejecta curtain radius, R, is R~5 km, and at 2 min, R~15 km To maximize the total integrated signal-to-background ratio over the maximum extent of time, the S-S/C should follow the impact by 8-10 minutes. The CBEIM and Centaur Separation Time

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