DEEP SPACE ONE: NASA’S FIRST DEEP-SPACE TECIINOLOGY VALIDATION MISSION Marc D. Rayman and David 11. Lehman Jet Propulsion Laboratory California Institute of Technology 4800 Oak Grove Dr. Pasadena, CA 91109 USA Under development for launch in July 1998, Deep Space One (IX 1 ) is the first flight of NASA’s New Millennium Program, chartered to validate selected technologies required for future low-cost space science programs. Advanced technologies chosen for validation on DS 1 include solar electric propulsion, high-power solar concentrator arrays, autonomous on-board optical navigation, two low-mass science instrument packages, and several telecommunications and microelectronics devices. Throughout the two year primary mission, the technology payload will be exercised extensively to assess performance so that subsequent flight projects will not have to incur the cost and risk of being the first users of these new capabilities. An important component of the DS 1 mission is diagnosing any in-flight anomalies or failures. Although DS 1 is driven by the requirements of the technology validation, it also presents an important opportunity to conduct solar system science. During the primary mission, the spacecraft will fly by asteroid 3352 McAuliffe, Mars, and comet P/West-Kohoutek-Ikemura. The two science instruments that are being validated, an integrated visible imager and UV and IR imaging spectrometer and a plasma physics package, will be used to collect science data during the cruise and encounters. In addition, a suite of fields and particles sensors included to aid in the quantification of the effects of the solar electric propulsion on the spacecraft and near-space environment will be used for science measurements complementary to those of the plasma instrument. The return of science data will demonstrate that the technologies are compatible with the demands of future scientific missions and will ensure that this rare opportunity to encounter such a variety of solar system targets during a short mission will be fully exploited. - INTRODUCTION NMP are not intended to be fully representative of the spacecraft to be flown in future missions, but NASA’S vision of space and Earth science the advanced technologies they incorporate are. in the early years of the next century comprises frequent, affordable, exciting, scientifically Although the objective of the NMP tech- compelling missions. Microspacecraft, small nology validation missions is to enable future enough to be launched on low-cost launch science missions, the NMP missions themselves vehicles, with highly focused objectives, will are not science-driven. They are technology- execute many of these missions. driven, with the principal requirements coming from the needs of the advanced technologies that The New Millennium Program (NMP) is form the “payload.” The missions will be high designed to accelerate the realization of these risk because, by their nature, they will incorporate missions by developing and validating some of unproven technologies that, in general, will not the key technologies they need,l Beginning in have functionally equivalent back-ups. Indeed, if 1998, NMP will flight validate high risk an advanced technology does not pose a high risk, technologies using dedicated deep-space and validation by NMP is not required. Earth-orbiting flights. The spacecraft flown by — Deep Space One (DS 1 ) is the first flight of Copyright 1997 by the American Institute of Aeronautics the NhfP. It is being led by JPL, with Spectrum and AStrOnWliCS, Inc. The U.S. Government has a royalty- Astro, Inc. as the partner for spacecraft frec liccnsc to cxcrcisc all rights un(icr the copyright development. Additional background on the New claimed herein for Govcmmcntal purposes. All other rights Millennium Program and the selection of arc reserved by the copyright owner. technologies and mission design for DS1 are given elsewhere.2 1 The success of DS 1 depends upon DS 1 ADVANCED TECHNOLOGIES determining how well any of these technologies will work on future missions. If an advanced The DS 1 project is validating 12 advanced technology fails on DS1, even if it leads to the technologies. These have been selected on the termination of the mission, as long as the failure basis of how relevant they are to NASA’s future can be diagnosed, the objective of validating the space science programs, how revolutionary they technology will be accomplished. If DS 1 could are, and how much the risk of their subsequent prove that an advanced technology is not use is reduced by validating them in spaceflight. appropriate for future missions, that is a valuable In addition, more practical issues such as schedule result. This information would achieve the goal and compatibility with the basic DS 1 mission of reducing the cost and risk to candidate future profile contributed to their selection. users of the technology. Of course, it is likely that such a determination would lead to The DS 1 advanced technology experiments mod ifications to the implementation of the are listed in Table 1. Overviews of the technology, thus restoring its potential value to technologies are given in the next section in the future space science missions. order in which they appear in the table. TECHNOLOGY OVERVIEW Advanced Technology I Overviews of the advanced technologies Solar electric~ropulsion selected for DS 1 follow. The mission in which the Solar concentrator array technologies will be validated is discussed in the Autonomou=optical navigation next section. Integrated camera and imaging s~ectrometer Solar electric Promlsion Integrated io~and electron spectrometer Solar electric propulsion (SEP) offers %all deep-~ace transponder significant mass savings for future deep-space and K.-band soiid state power amplifier Earth-orbiting missions with high Av Beacon monitor operations requirements. The objective of the NSTAR ~utonomous remote agent (NASA SEP Technology Application Readiness) Zow power electronics program3, to validate low-power ion propulsion, ~ower actit~lon and switching module fits well with NMP’s goals. The joint JPL/Lewis Multifunctional structure Research Center effort, which was started in November 1992, has been building and ground Table 1. DS 1 Advanced Technologies. testing ion propulsion hardware in parallel with fi~bricating flight hardware for DS1. NASA requires that DS 1 validate the first four technologies, with the rest being designated The NSTAR-provided ion propulsion mission goals. To reach the asteroid, Mars, and system (IPS) uses a hollow cathode to produce comet, those required technologies and the small electrons to collisionally ionize xenon. The Xe+ is deep-space transponder must function. Of electrostatically accelerated through a potential of course, the primary objective of the project is to up to 1280 V and emitted from the 30-cm thruster validate technologies, and most of the through a molybdenum grid. A separate electron technologies on DS 1 will be nearly or completely beam is emitted to produce a neutral plasma beam. validated during the first few months of flight, The power processing unit (PPU) of the IPS can well before any of the encounters. Some of the accept as much as 2.5 kW, corresponding to a other technologies provide enhancements in the peak thruster operating power of 2.3 kW and a execution of the mission. Although science is not thrust of about 90 nlN. Throttling is achieved by the prinmry goal of the mission, returning science balancing thruster and Xe feed system parameters data is an important part of the overall at lower power levels, and at the lowest PPU demonstration that all technologies are consistent input, 600 W, the thrust is about 20 nlN. The with a mission that conducts science. specific impulse decreases from 3300s at peak power to about 1900 s at the minimum throttle level. 2 Because the purpose of flying NSTAR’S single-axis gimbal ensures pointing in the more IPS is to validate it for future space science sensitive longitudinal axis. DS1 will be the first missions, a comprehensive diagnostic system is spacecraft to rely exclusively on concentrator also on the spacecraft. This will aid in arrays; it also is the first flight to use only quantifying the interactions of the IPS with the multibanclg:ip cells. remainder of the spacecraft, including advanced- technology science instruments, and validating Autonomous optical naviga~ models of those interactions. The diagnostic Because operations are a significant cost in instrument suite includes a retarding potential NASA science missions, NASA explicitly in- analyzer, two Langrnuir probes, search-coil and. cluded autonomy in its guidelines to NMP. A fluxgate magnetometers, a plasma wave sensor, reduction in requirements for Deep Space and two pairs of quartz-c~stal microbalances and Network (DSN) tracking of spacecraft will come microcalorimeters. One of these pairs has a direct from the placement of a complete navigation view of the ion beam, while the other is shadowed capability onboard the spacecraft.5 (Other by spacecraft structure. Measurements will autonomy technology experiments are discussed include the rate and extent of contamination below.) The autonomous system to be validated around the spacecraft from the Xe+ plume and the on DS 1, AutoNav, will navigate the spacecraft sputtered Mo from the grid, electric and magnetic from shortly after injection through the encounters fields, and the density and energy of electrons and using data already resident on the spacecraft or ions in the vicinity of the spacecraft. In addition, acquired and processed onboard. Stored in the sensors will be used to complement science AutoNav will be the trajectory generated and measurements of DS 1‘s ion and electron optimized on the ground; the ephemerides of the spectrometer (see below), particularly during the DS 1 target bodies, about 250 distant “beacon” encounters. asteroids, and all planets except Pluto; and a catalog of the positions of 250,000 stars (all Solar concentrator arrav contained in the Tycho catalog).