Lunar CRater Observation and Sensing Satellite Project LCROSS Astronomer Workshop Feb. 29, 2008 NASA/ARC, Mountain View, California Mission Design & Observation Campaign Constraints Ken Galal/ARC

LCROSS Mission Design & Observation Campaign Constraints 2 LRO/LCROSS Launch Dates Launch Requirements LCROSS launch dates set by LRO  Driven by LRO sun beta angle constraint at lunar solstices  Launch blocks consist of daily launch opportunities over 3-4 consecutive days  ~2 weeks between each launch block  +/-30 minute maximum launch window with launch possible on 10 minute centers  Currently 18 possible launch dates identified from Oct. 28 to Dec. 25 (additional dates in December under consideration)

LCROSS Mission Design & Observation Campaign Constraints 3 Nominal LCROSS Launch Blocks Current Range of Launch/Impact Opportunities [a subset may be chosen that best satisfies LCROSS propellant and observation constraints] Preliminary LRO Launch Blackout Time

LCROSS Mission Design & Observation Campaign Constraints 4 Driving Mission Requirements Impact Conditions:  |V| > 2.5 km/s  Impact angle > 60 deg relative to horizontal  Impact targeting accuracy of ±10 km, with a goal of under ±1.75 km Impact Observation:  Crater sun & Earth tilt angle <90 deg (angle from normal to crater floor to sun/Earth)  DSN 70m station coverage required for LCROSS science data collection  Ground observatory elevation angle >45 deg  Lunar phase >30 deg from new or full moon  Impact time occurs when observatory is minimum of 2 hrs from dawn/dusk (with a goal of >3hrs)

LCROSS Mission Design & Observation Campaign Constraints 5 Ground Observatory Impact Geometry Observatory Lunar Phase & 2 hr Dawn/Dusk Lighting Constraint Observatory Viewing Elevation Constraint +   ≥ 30°  ≥ 45° Incoming Sunlight Resulting impact lunar phase exclusion zones

LCROSS Mission Design & Observation Campaign Constraints 6 Sample Impact Geometry Sample Impact Viewing Geometry for Nov. 24 (3.5M, 0-P30 launch window) or Dec. 9 (3M) Launch Dates

LCROSS Mission Design & Observation Campaign Constraints 7 Crater Impact Geometry Sun tilt angle (in blue) –Key for ejecta cloud lighting –Yearly variation due to 1.5° inclination of lunar equator relative to ecliptic plane –Additional monthly variation function of crater latitude (larger amplitudes away from pole) Earth tilt angle (in green) –Key for observatory viewing –±6.7° Monthly variation of due to inclination of lunar equator wrt lunar orbit plane  For a given impact date, lighting and viewing geometry varies greatly from crater to crater

LCROSS Mission Design & Observation Campaign Constraints 8 Target Impact Conditions Baseline Candidate Craters: Faustini, Shoemaker, Cabaeus & Shackleton Crater Incident impact angle: >60 deg Impact velocity: 2.5 km/sec

LCROSS Mission Design & Observation Campaign Constraints 9 Driving Mission Constraints Mission Lifetime:  <120 days (limited by LV separation system qualification and budget!) DV Capacity:  A maximum of 50 m/s allocated to re-targeting of LCROSS by launch vehicle post-LRO separation  A maximum of ~135 m/s available to establish LCROSS orbit and to adjust impact time by up to +/-12 hours Navigation:  Impact targeting precludes performing large orbit maneuvers (e.g., to alter impact time or target a different crater) too close to impact DSN Scheduling:  DSN 70m station at Canberra is scheduled to be unavailable for support for 6 months starting 10/08 (scheduled maintenance)  DSN 70m station at Madrid is scheduled to be unavailable for support for 6 months starting 4/09

LCROSS Mission Design & Observation Campaign Constraints 10 Mission Design Process Candidate impact targets & observatories Satisfy Req & Constraints? No Yes Science/Obs Requirements Candidate LRO launch dates Candidate trajectories Calculate Impact Geometry & DV Requirements Baseline trajectory & Impact Date/Time Refine Inputs Mission Constraints Navigation Considerations

LCROSS Mission Design & Observation Campaign Constraints 11 Family of LCROSS Trajectories 3 Month Cruise (3:2 resonance) Baseline Trajectory 3 Lunar orbits about Earth (27 day period) 2 LCROSS orbits about Earth (~40 day period), ~86-day total mission Southern swingby, Southern impact 3.5 Month Cruise (3.5:2.5 ratio) 3.5 Lunar orbits about Earth (27 day period) 2.5 LCROSS orbits about Earth (~38 day period); ~100-day total mission Northern swingby, 180 deg change in lunar phase from 3M 4 Month Cruise (4:3 resonance) 4 Lunar orbits about Earth (27 day period) 3 LCROSS orbits about Earth (~36 day period); ~114-day total mission Southern swingby 27 deg change in lunar phase from 3M 3-Month Trajectory 3.5-Month Trajectory4-Month Trajectory

LCROSS Mission Design & Observation Campaign Constraints 12 Launch & Impact Date/Time General Guidelines Each impact date will have a fixed nominal impact time and target crater Trajectories within a 3-4 day launch block will use the same trajectory type (i.e., 3M, 3.5M or 4M) and have impact dates within a few days of each other Trajectories within a +/-30 minute launch window on a given launch day may have different impact dates (by no more than 1 day) Trajectories associated with different launch blocks can have the same impact date/times Once launched, nominal impact time will be targeted, but offsets of a few minutes may be allowed (i.e., a cutoff in impact time adjustments will occur several weeks before impact) Late December launch dates may drive us to using a 2.5M trajectory due to poor geometry

LCROSS Mission Design & Observation Campaign Constraints 13 Common LCROSS Impact Dates LRO Launch Blackout Time