#'j ._ Final Report NAG3-1648 L?7.'" 7 _.,-.... Collaboration on SEP Missions to the Moon and Small Bodies The collaboration of Dr. Carle M. Pieters was part of a project that developed rational and a detailed mission scenerio to explore the Moon and an extinct comet. Dr. Pieters' involvement focused on evaluating spectroscopy instruments and defining a mission plan to derive maximum science return. Attached are two reports that document this activity. LPSXX'VI 1201 THE DIANA DISCOVERY MISSION: A SOLAR ELECTRIC PROPULSION MISSION TO THE MOON AND A COMET; C. T. Russell, IGPP/UCLA; J. Abshire, GSFC; M. A'Hearn, U. Maryland; C. Alexander, A. Konopliv, A. Metzger, JPL; J. Arnold, UCSD; J. J. Berthelier, CETP; R. Elphic, LANL; M. Hickman, D. Palac, LeRC; R. Jaumann, G. Neukum, DLR; T. McCord, U. Hawaii, R. Phillips, U. Washington; C. Pieters, Brown University; W. Purdy and R. Rosenthal, TRW. In response to the Discovery announcement of opportunity a team consisting of TRW, Lewis Research Center, JPL and UCLA with scientific co-investigators from government and University laboratories have proposed to fly the first planetary solar electric propulsion (SEP) mission. Diana is designed to carry an X-ray and gamma ray spectrometer, an imaging spectrometer, a framing camera, a laser altimeter an ion spectrometer and a magnetometer. In order to obtain lunar gravity data from the far side of the moon a relay satellite is placed into high polar orbit about the moon to relay the Doppler-shifted telemetry to Earth. Diana will spend two months in a 700 km polar orbit obtaining mineralogical data from a full spectral map of the lunar surface, and then spend a year in a 100 km (or below) polar orbit mapping the lunar elemental composition, its topography, gravity field, ions from its atmosphere and its permanent and induced magnetic fields. After the low altitude mapping phase the ion thrusters propel the spacecraft out of the lunar sphere of influence and onto a heliocentric trajectory to rendezvous with dormant comet Wilson-Harrington. The ground truth provided by the returned lunar samples to validate the remote sensing instruments for lunar studies will also serve to validate the Wilson-Harrington observations since the same instruments will be used at both bodies. The value of solar electric propulsion to the planetary program is made evident by comparing the same mission attempted with solely chemical propulsion. Diana is launched with a Delta II launch vehicle. A similar chemical mission would require a Titan IV and would be i:,_,, in the Cassini class of missions. Solar electric propulsion will open up exploration of the inner solar system including the main belt asteroids by making many bodies accessible at an affordable •-_;_:cost. Comet Rendezvous and Orbit Phase .,¢_ Events Trans- Delta launch Heliocentric Chemical LOI Pha_"_-_._ 4000 km Lul_u.Phlme SEP spiraldown 100km _ subsatellite orbit Sub,satellite release Science Ops at700 km Science Ops al100 km 7sceI(_k.m _ _- _J_"_ N SEP spirale_ea'_rr_ Phase SEP transfer tocomet Multiple thrust and coast arcs Cometan/rendezvous Multiple comel flybys 10 daycomet orbits 2day comet orbCs _Launch and Transfer Phase Diana Fact Sheet Mission Summary Diana is a Discovery mission that ,,,,,ill provide high priority geo- physical and geochemical science data on two solar system targets: an evolved body. the Moon. and a primitive body. the nucleus of thc dormant comet P/Wilson-Harrington. Diana will conduct a compre- hensive orbital survey of these two bodies, and compare and contrast complementar2, .' data sets. Diana returns prime data immediately after launch and. with the two-missions-in-one aspect, has a high science return per dollar. Diana will apply new technologies to scdar system exploration, in particular xenon ion solar electric propulsion (SEPt. An excellent vehicle for public awareness and educational activities, the Diana outreach program involves element,'u-y./middle_igh schools, commun- ity colleges. HBCUs, Mission Description The Diana launch is September 15, 2000. Lunar orbit insertiola is Flight System accomplished with chemical propulsion. SEP is used for orbit circular- The flight system spacecraft bus is a direct descendent of NASA's ization and achievement of three separate altitudes: 4(XX)km for relay Lewis SSTI spacecraft. The SEP module uses components brought t(_ subsatellite deployment. 700 km for a two month su_'ey, and 1(_ km flight readiness on NASA's NSTAR and APSA programs. Key for aone year mapping mission. characteristics are: After the lunar mission is complete, SEP is used to raise the orbit • Mass: 658 kg dO' mass. 450 kg xenon propellant capacity. 102 kg altitude to escape, transfer to a heliocentric orbit, and rendezvous with hydrazine and 65 kg oxidizer capacity the comet at a solar distance of 1.9 AU. The mission ends after six • Power: solar array 7 kW @)IAU BOI.. 500 W (.a'3.3A1 t. 65 W/kg: months of operations in the vicinity of the comet, at distanccs of 3.2 batter3.' 16 A-hr dual ceil NiH AU solar and 3.5 AU to Earth. • Propulsion: six 450-2300 W 30 cm xenon ion electric engines, lk_ttt Mission Objectives bipropcllant 38 N _mdeight monopropellatn 4N thrusters Lunar objectives (Lunar Exploration Science Working Group priorities): • Ctm'mlunications: 2.2 Mbps (hmar) to 30 kbps (3.5 At;)at X-band • Constrain models of lunar origin by estimating the refractor3_, element over 1.5 m HGA through 50 W TWTA content and ratio of magnesium to iron in the crust Schedule • Estimate the composition and structure of the lunar crust in order to CY q4:gS:96:g7 _,'¢, qt) 0(11t)1 02 (13 04105106: model its oriDn and evolution Analysis and Definition i *Determine the origin and nature of the lunar magnetic field and esti- Design and Fabrication ........ mate the size of the lunar core Integration and Launch •Determine the nature of impact processes over geologic time and how Lunar Mission Operations ..... they have modified the structure of the crust Heliocentric Transit ..... • Determine the nature of the lunar atmosphcrc and the physical basis Comet Mission Operations: for its sources and sinks Schedule Reserves: design/development, net 9U days, distributed to Cometary. objectives (National Academy of Science andNASA studies): activities; lunar orbit operations/heliocentric transit, net 25 days *Determine the mass and density of the comet •Map the structure and composition of the mantle - Determine the refractory/volatile ratio in the nuclcus • Determine the surface morphology and structurc • Measure the organic content of the crust •Measure the volatile composition and the outgassing rate • Determine how the nucleus interacts with the solar wind Science Payload Diana Mission Mana[ement Investigation Instrument Team Leader Mass (kg) Power (W) NASA Discover,.' Program Manager: Mark Saunders NASA Discovery Program Scientist: Henry Brinton Framing Camera G. Neukum, DLR 4 7 Diana Principal Investigator: Chris Russell. UCI.A 1310-g25-3188 Imaging Spectrometer C. Pieters, Brown U 14 42 Diana Project Manager: Brian Muirhead. JPL (818- 393-1013 Gamma-Ray/Neutron A. Metzger, JPL I0 8 Diana Deputy Project Manager: Don Palac. LeRC (216-977-7094) Spectrometer Diana Government/Industry Team X-Ray Fluorescence A. Metzger. JPL 12 Jet Propulsion Laboratory: project management: mission operations Spectrometer NASA Lewis Re.arch Center: Phase A/B stud)' management: mission Laser Altimeter J. Abshire, GSFC 8 5(I design: science instrument acquisition Magnetometer C. Russell, UCLA 3 3 TRW Space & Electronics Group: flight system development, Ion Mass Spectrometer R. Elphic. LANL 7 8 integration and test: launch and operations support Relay Subsatellite A. Konopliv. JPI. 25 197 Jackson and Tull (an SDBC): Relay Subsatellite design, fabrication, (Gravity Science) assembly and test, and flight system support 9402013 TIIOc Use ordisclosure of data contained onthis page issubject to the restriction on the lille page ofthis proposal