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). Because of the IPS, DS 1 requires a high power solar array. The Ballistic Missile Defense Throughout the mission, one to two times Organization, working with NASA’s Lewis per week, AutoNav will be invoked by the Research Center and AEC-Able Engineering, operating sequence to command the attitude Inc., wants space validation of its Solar control system to turn the spacecraft to point Concentrator Arrays with Refractive Linear sequentially at 4 to 20 beacons. Visible-channel Element Technology (SCARLET 11)4, so flying images from the integrated camera and imaging SCARLET on DS 1 is mutually beneficial. A 180- spectrometer (see below), each with one beacon W SCARLET I array, using similar technology, asteroid and known background stars, are was included on the METEOR commercial acquired. On-board image processing allows experiment platfoxm, which was destroyed in a accurate extraction of the apparent position of each failed Conestoga launch in October 1995. asteroids with respect to the stars, thus allowing the spacecraft location to be estimated. The SCARLET uses cylindrical silicone Fresnel heliocentric orbit is computed with a sequence of lenses to concentrate sunlight onto these position determinations combined with GaInP#GaAs/Ge cells arranged in strips with an estimated solar pressure, calculated gravitational expected average efficiency of over 22~o. perturbations, and on-board knowledge of the Including the optical efficiency of the lenses, a thrust history of the 11?S and incidental total effective magnification of 7.14 is achieved. accelemtions from unbalanced turns by the With relatively small panel area actually covered reaction control systetm The trajectory then is by solar cells, the total cost of cells is lowered and propagated to the next encounter target, and thicker cover glass becomes practical, thus course changes are generated by the maneuver reducing the susceptibility to radiation. The dual design element. In general, those course changes junction cells display significant quantum will be implemented through changes in the IPS efficiencies from 400 nm to 850 nm. thrust direction and duration, but in certain cases described below, the maneuvers may be The pair of arrays will produce 2.6 kW at 1 accomplished with the small chemical propulsion AU at the beginning of life. Each array comprises system. four panels that are folded for kiunch, and a Intem-ateci camera and imazin~ spectrometer PEPF measures the energy spectrum of Low-mass science instruments clearly are electrons and ions from 3 eV/q to 30 keV/q with a critical for future space science missions. One of resolution of at least 5%. instead of using the advanced technologies DS 1 will wilidate is the moving parts, it electrostatically sweeps its field Miniature Integrated Camera-S pectron~eter of view, achieving :ingular resolution of 45° in its (MICAS), conceived and developed by a team azimuth and 5° in elevation. PEPE also measures from the United States Geological Survey, SSG, ion mass in the range of 1 to 135 amu perunit Inc., the University of Arizona, and JPL. In one charge with a resolution of 5%. 12-kg package, this derivative of the original concept for a Pluto Integrated Camera PEPE will serve three functions on DS 1. It Spectrometer includes two visible imaging will validate the design for a suite of plasma channels, an ultraviolet imaging spectrometer, and physics instruments in one package; it will assist an infrared imaging spectrometer plus al 1 the in determining the effects of the IPS on spacecraft thermal and electronic control. All sensors share a surfaces and instruments and on the space single 10-cm-diameter telescope. With a structure environment, including interactions with the solar of highly stable SiC, no moving parts are wind; and it will make scientifically interesting required. Spacecraft pointing directs individua] measurements during the cruise and the encounter detectors at the desired targets. with the comet and Mars (and possibly the asteroid). Indeed, a key investigation of DS1 will The instrument includes two visible be whether space physics measurements can be detectors, both operating between 500 and 1000 made from a spacecraft operating with an ion nm: a 1024 x 1024 CCD with 13 ~rad pixels and a propulsion system to assure future users that there 256 x 25618 prad per pixel CMOS active pixel are no incompatibilities. The high mass resolution sensor, which includes the timing and control of PEPE enables it easily to distinguish between electronics on the chip with the detector. The two the two major species emitted by the IPS, Xe and imaging spectrometers operate in push-broom Mo. mode. The UV spectrometer spans 80 to 185 m-n with 2.1 nm spectral resolution and 316 prad Telecommunications technolo~ies pixels. The IR spectrometer covers the range DS 1 will validate a small deep-space from 1200 to 2400 nm with spectral resolution of transponder (SDST), built by Motorola, and a K,- 12 nm and 53 ~rad pixels. band solid state power amplifier developed by l.ockheecl Martin. Combining the receiver, MICAS will serve three functions on DS 1. command detector, telemetry modulation, First, as with all the advanced technologies, tests exciters, beacon tone generation (see below), and of its performance will establish its applicability to control functions into one package of about 3.2 future space science missions. Second, the kg, the SDST allows X-band uplink and X-band visible CCD channel will be used to gather images and I$:band downlink. The K,-band signal is for the AutoNav’s use. Third, it will collect amp]lfled by the 0.6 kg power amplifier, which valuable science data during this mission at the generates 2.6 W output with an overall efficiency asteroid, Mars, and comet. of 1370- 15910. The SDST supports both uplink and dowrdink radio science modes of operation, Interzrated ion and electron s~ectrometer and it provides coherent and noncoherent op- Just as MICAS integrates several different eration for radio navigation purposes (in addition measurement capabilities into one low-mass to basic communications). To achieve the package, the Plasma Experiment for Planetary SDST’S functionality without a new technology Exploration (PEPE)T combines multiple development woLlld require over twice the mass. instruments into one compact 6-kg package. Built This compact, low-mass transponder is enabled by Southwest Research Institute and Los Alamos by the use of advanced CiaAs monolithic n~icro- National Laboratory, PEPE detemlines the three- wave integrated circuits, high density packaging dimensional plasma distribution over its 2.8x sr techniques, and silicon ASICS. Such field of view. The instrument includes a very low telecorl]r~lLlllic:itions advances for future missions power, low mass microcalorimeter, provided by are described in more detail elsewhere.g Stanford University, to help understand the plasnla/surface interactions Beacon monitor operaticms
4 The SDST generates the four tones needed reissues or modifies them if the response is not for beacon monitor operations, conceived to what was tinticipated. reduce the large demand that would be expected on the INN if many missions were in flight The design is flexible enough to handle a simultaneously, as envisioned by NASA. In variety of unexpected situations onboard, and its beacon monitor operations, an on-board data access to a much more complete description of the summarization system detemlines the overall spacecraft state than would be available to ground spacecraft health and selects one of four tones to controllers in a traditional operations concept transmit to indicate to the ground operations team allows it to make better use of on-board what action, if any, is necessary. Without data resources. A mode identification and modulation, these tones are easily detected with reconfiguration engine allows recovery or work- small, low-cost systems on Earth, reserving the arounds in the presence of faults without requiring more expensive large DS N stations for command help from the ground except in extraordinary radiation and data reception when the beacon cases. Several faults will be simulated during the indicates that such services are needed. The four remote agent experiment cm DS 1. tones correspond to the spacecraft not needing any assistance because all is well; informing the h4icroelectronics and structures ground that there was a problem that the space- Electronics mass, volume, and power craft resolved; alerting the ground that the space- consumption are important drivers for overall craft has data that are ready to be transmitted, so a spacecraft design. DS 1 includes tests of two DSN pass should be scheduled; and requesting microelectronics technologies and an assistance because the spacecraft has encountered mechanical/electronic experiment intended to a problem it was unable to solve. Experiments to contribute to the achievement of NASA’s vision be conducted during the mission include not only of spacecraft in the future. To reduce the power the data summarization and tone generation and consumption of electronics, one experiment uses detection, but also DSN responses. Beacon devices with very low voltage and low monitor operations may be used during DS 1 to aid capacitance.]l This low-power electronics in ensuring that the IPS is operating between experiment contains a ring oscillator, multipliers, scheduled DSN communication sessions. and discrete transistors to test 0.9-volt logic and 0.25-pm gate lengths (achieved with 248-rim Autonomous remote agent lithography). Provided by the Massachusetts The autonomous operations capability DS 1 Institute of Technology Lincoln Laboratory, this will validate represents an entire architectural experiment will validate the performance of these approach that is expected to be applicable to a devices throughout the life of the mission, with wide range of future science missions.10 The particular interest in the effects of radiation. DS 1 team developing this system is drawn from JPL, also will test a power activation and switching Ames Research Center, and elsewhere. Rather modu]e12, the result of a joint development among than standard remote control, this approach uses Lockheed Martin, Boeing, and JPL. This device an agent of the ground team onboard the contains two sets of four power switches, each set spacecraft. This remote agent will be tested in a controlled by its own mixed signal ASIC, restricted case on DS 1, in preparation for more providing current limiting and current and voltage ambitious experiments on subsequent flights. The sensing. High-density packaging technology remote agent includes an on-board mission qu~dnlples the packing density over the current manager that carries the mission plan, expressed state of the art. Designed to be capable of as high-level goals. A planning and scheduling switching up to 40 V and 3A, the PASM as an engine uses the goals, comprehensive knowledge experiment will switch an internal test load on of the spacecraft state, and constraints on Dsl. spacecraft operations to generate a set of time- based or event-based activities, known as tokens, A multifunctional stnlcture13, provided by that are delivered to the executive. The executive the United States Air Force Philips Laboratory expands the tokens to a sequence of commands and Lockheed Martin Astronautics, is that are issued directly to the appropriate incorporated as an experiment. This new destinations on the spacecmft. The executive packaging technology combines load-bearing monitors the response to these commands and elements with electronic housings and themlal control, thus greatly reducing the mass of
5 spacecraft cabling and traditional chassis. The collaboration with NASA’s Marshall Space Flight DS 1 experiment will return d:ita on the Center and Johnson Space Center, will be performance of the electronic connection systems mounted on the second stage, which accomplishes for embedded test devices and the thermal control insertion into Earth orbit. After the second stage’s for a test panel incorporating such a second bum, to raise the orbit of the third stage multi functiomd structure. and DS 1, the stage separates and carries SEDSAT- 1 to its intended orbit, where it is MISSION separated. The third stage completes DS 1‘s injection to heliocentric orbit. NASA directed that 1)S 1 encounter one asteroid and one comet during its primary An overview of the trajectory for launch at mission. It was decided early in NMP that a the beginning of the launch period is shown in complete validation of the technologies would Figure 1. Some details will change by a few require flying them on missions that bore strong days, depending upon the final performance resemblance to science missions of the future. realized for the IPS and SCARLET (and when DS 1‘s mission was focused on small bodies during the ]aunch period the launch occurs). After because of the great interest in exploring them in injection, two weeks will be spent performing future missions, the ease in reaching some for this initial evaluation of the spacecraft, with focus on validation flight, and the desire to conduct a basic spacecraft health as well as those functions mission that NASA’s principal customer (the needed for the long duration IPS thrusting. The United States taxpayers) would find exciting. solar arrays, transponder, IPS, AutoNav, and MICAS visible channel are the technologies that Another cons~aint on the mission derives will receive the early attention. Ground-based from the need to return results promptly to the determination of the actual trajectory after injection future users. Except for tests of lifetime, most will be combined with results of the first technologies could be evaluated on short missions SCARLET and IPS tests to generate and optimize as well as long ones, so it was decided that the an updated low-thrust trajectory that will be primary mission should last no longer than about transmitted to the spacecraft. Thereafter, the two years. This would allow sufficient time to baseline plan is for all navigation to be conduct an exciting mission and to exercise the accomplished exclusively by the on-board technologies under a wide range of conditions autonomous navigation system. Conventional without forcing eager potential users to wait radio navigation will be used to validate the unreasonably long before being confident about performance of AutoNav. their use. NASA has strongly supported a high risk mission for DS 1 (and the other NMP Fifteen days after launch (L+15), the IPS missions), and it has encouraged the project to will begin an 11-day thrust period. With the develop plans for a particularly bold and exciting spacecraft in constant communications with the extended mission. DSN, this will provide the first opportunity to gain experience with the IPS for deterministic DS 1‘s launch period extends from July 1 to thrust. A 5-day gap in thrusting from L+26 to July 31, 1998, with the opening dictated L+30 is designed to allow time to activate PEPE principally by spacecraft readiness. It will launch (after spacecraft outgassing has reached acceptable on the first McDonnell Douglas Aerospace Delta levels), deploy the protective, UV-opaque cover 7326-9.5, the smallest vehicle in the Delta stable, on MICAS, and recover from anomalies. and will be the first launch of NASA’s Med-Lite program. This launch vehicle was selected largely The mission and trajectory designs account on the basis of prompt availability and low cost, for regular suspensions in IPS thrusting. (he to but its capability exceeds what is needed for DS 1, two times per week (and more frequently prior to with relatively low mass and low injection energy encounters) the spacecraft will turn to collect its (in part attributable to the high performance of the optical navigation images. During times of IPS IPS). The residual launch vehicle performance thrusting, this will require the spacecraft to turn has allowed the manifesting of another spacecraft away from the dlrLISt vector. The IPS thruster on this launch. SEDSAT- 1, built by the Students gimbal allows pointing of the thrust vector for the Exploration and Development of Space at through the spacecraft center of mass, but the the University of Alabama in }Iuntsville, in spacecraft attitude during IPS thrust is fixed by
6 the need to achieve thrust in a particular direction cycle as possible, DSN contact will be and to keep the solar arrays normal to incident accomplished through one of the three low gain sunlight for maximum power. In addition, some antennas whenever the lower antenna gain is DSN passes will use the body-fixed X-band high sufficient. Besides the predictable hiatuses in II% gain antenna, requiring the spacecraft to point it at thrust, anomalies that prevent thrusting are Earth. To maintain as high an IPS thrusting duty accounted for by designing for a lower duty cycle.
+..000~o.”oo””+,:::,A, 6121GQ .,/A_.
Figure 1. DS1 trajectory. The solid line indicates the IPS thrust is on; the dotted portion is for ballistic coast. The tic marks are at 30-day intervals, During most of the mission, one 8-hour Sequences will operate for 4 weeks during DSN pass each week will allow commanding and most of the mission. The small ground team return of spacecraft health and technology makes extensive use of existing tools and services validation data. Because of the importance of JPL has developed to support a wide range of maintaining IPS thrust, at least one shorter pass is missions. With these and standards such as scheduled between the longer ones. Conducted CCSDS (Consultative Committee for Space Data only with one of the low-gain antennas to allow Standards), the ground segment’s cost is kept to a communication during thrusting, this pass will minimum. reveal whether the IPS is thrusting as expected and provide an opportunity to begin recovering Throughout the cruise, most of the tech- from anomalies with minimal loss of thrust time. nologies will be exercised. Some simply will require regular activation and checks of their
7 health. Others, such as the solar arrays and resolution for visible images is expected to be in telecommunications technologies, will require the range of 1 m to 5 m per pixel. spacecraft maneuvers to evaluate their perform- ance under different Sun or Earth viewing angles The asteroid encounter will allow an and thermal conditions. Certain times are devoted opportunity to gather science data on the size, to specific validation activities that affect other shape, spin state, geotnorphology, albedo, and subsystems, such as the remote agent experiment, the mineralogy of the surface material and its which will control other parts of the spacecraft compositional heterogeneity. It also may be during its tests. Many of the technologies will be possible to measure or, at least constrain, the used as part of the execution of the basic mission. magnetization and the interaction of the body with the solar wind, including sputtering. The final On January 19, 1999, the spacecraft will science plans for the encounter will be developed encounter 3352 McAuliffe at 7.8 km/s. This S- in early 1998. type Earth-approaching asteroid is estimated to be 1 km in radius. During the final 20 days of the The deterministic thrust resumes 4 days after spacecraft’s approach to the body, AutoNav will the closest approach, by which time essentially all require optical navigation images and trajectory science and technology validation data from the correction maneuvers at an increasing frequency encounter will have been returned. This thrust arc to control the targeting of the final encounter. lasts for approximately 340 days. By the end of These small maneuvers may be conducted with the thrusting, the spacecraft will have expended the IPS or the hydrazine reaction control system about 75 kg of Xe (for deterministic thrust as well (RCS). The RCS will be used for the maneuvers as navigational needs, specific IPS validation during the final day to save time; it may be used in experiments, and two-axes of attitude control), earlier maneuvers if the calculated r-maneuver providing a total velocity change of about 3.6 duration exceeds the time allocated for the IPS. kntis. The decision will be made onboard. In addition, if thrust is required in an attitude that is disallowed In April 2000, DS 1 encounters Mars for a by the attitude control system, it will be modest gravity assist. This event provides a decomposed into two allowed maneuvers without bonus opportunity to conduct additional ground intervention. technology validation and science data acquisition with MICAS, PEPE, AutoNav, and the IPS Because the size and shape of McAuliffe diagnostics sensors at Mars. The flyby speed is are not well known, a flyby altitude of 10 km is 3.4 kntis. The ahitude may be adjusted to planned, With an expected navigational delivery improve mission performance, but the baseline is accuracy of better than 3 km, this assures a safe 10,000 km from the planet’s center. Depending but very exciting encounter. The last opportunity upon mission resources, an encounter with for a trajectory correction maneuver will be 3 Phobos or Deimos is possible. hours before closest approach. If previously enabled by ground command, AutoNav, based on In June 2000, DS 1 reaches comet its analysis of the approach images, will make a 76P/West-Kohoutek-Ikemura, a few weeks after detem~ination if a closer encounter is safe. If it is, the comet’s perihelion. AutoNav will use images a “bold maneuver” will be executed autonomously initially of the coma and finally of the nucleus to to reduce the closest approach altitude to 5 km. calculate corrections to the trajectory for a close During the final approach, AutoNav’s MICAS flyby. With an encounter speed of 14 krrds, images will be interspersed with MICAS images science data at the comet that may be collected and spectra collected for science purposes. The include the structure and composition of the coma late navigation images will contain infomlation and tfiil (including gas, plasma, and dust), the AutoNav nee& to provide rapid updates to its nature of jets and their connection to sufrace estimates of the range to McAuliffe, critical for features, the interaction with the solar wind, and keeping the asteroid in MICAS’ field of view. the same kind of characterization of the nucleus as Because h41CAS is body-fixed, the sufi~ce at the asteroid. The cometary environment is resolution achieved will be limited by when the highly uncertain, as is the response of the angular rate of the body exceeds the attitude spacecraft to debris. The current baseline is for a control system’s capability to keep h4cAuliffe in 500-km flyby, although substantial work on the the h41CAS boresight. The highest surface final encounter plans remains.
8 iiid in reaching the hydrazine and xenon lines The primary mission ends with the when the spacecraft is in the launch vehicIe completion of the return of data from the comet payload fairing. Thermal control is accomplished encounter. Solar conjunction in ]ate June 2000 with standard multilayer insulation, heaters, and will interrupt the data transmission for about two radiators. weeks but may afford an opportunity for radio science. Attitude control sensors include a stellar reference unit and inertial measurement unit for If the spacecraft is healthy and project nomlal operations, and a sun sensor for use in resources permit, an extended mission will be contingencies. A hydrazine reaction control attempted. Subsequent encounter targets will be system provides three-axis stabilization (when the investigated; test cases have suggested that an IPS is not thrusting) and can be used for small additional asteroid encounter may be possible, and course changes as described above. During IPS comet encounters and a return to the Earth/moon thrusting, the IPS thruster is gimbaled to control system will be considered. All of these options two axes, with the RCS providing control around wiIl depend upon the trajectory during the primary the thrust axis. mission; with the new technology IPS, SCARLET, and AutoNav, and their Most of the electronics are enclosed in the corresponding performance uncertainties, detailed integrated electronics module with a VME extended-mission planning must await more backplane, and most remote devices communicate information from the primary mission. During the over a 1553 bus. extended mission, extremely stressing tests may be conducted of the advanced technologies that are The IPS PPU requires high voltage for its not reasonable during the primary mission. The operation. The output from the solar arrays is operation of the spacecraft may be turned over to 100 V, and this power is fed directly to the PPU; students. a converter provides regulated 33 V to the
spacecraft bus. A 24 A-hr NiH2 battery, provided SPACECRA~ by the U. S. Air Force/Phillips Laboratory, provides energy between launch and first light on Clearly there are not enough advanced the solar arrays and supplements the solar array technologies on DS 1 to compose an entire power during IPS thrusting to cover transients in spacecraft. Because the focus of NMP is on the the spacecraft’s power consumption. The battery validation of these technologies for future also will be used if encounter geometry requires missions, not on building complete spacecraft that the arrays be too far off-Sun for them to representative of those to be used in future science power the spacecraft. missions, the remainder of the spacecraft utilizes existing low-cost components. As part of the The total injected mass is about 475 kg, agreement with NASA that this will be a high- comprising the 375 kg spacecraft, 25 kg of risk, low-cost mission, the spacecraft is hydrazine, and 75 kg of Xe. The spacecraft principally single string with Class B parts. The configuration is shown in Figure 2. design includes limited internal redundancy in some devices, and some functional redundancy at CONCLUSION the subsystem level. Wherever possible, standard inter~aces are used. The spacecraft design is The flight of DS 1 will provide extensive driven by the needs of the advanced technologies data useful for the validation of technologies and the technology-driven mission design. important for NASA’s vision of space and Earth science missions of the future. Indeed, important The spacecraft structure is an aluminum progress on these technologies has already been space frame based on the three Miniature Seeker made because of the work necessaxy to Technology Integration (MSTI) spacecraft built by incorporate them into a space mission. This Spectrum Astro, Inc. for BMDO. With most of impetus has provided ~he technology teams the components mounted on the exterior of the valuable insight into implementation issues that bus, their accessibility simplifies replacement would not be expected to arise in typical during integration and test. Because the technology development or conceptual mission spacecraft diameter is small, a boom is included to studies. In addition, spacecraft, mission, and
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power distribution unit Inertial measurement-- unit t l=.Intcerated . . . . . electronics module Multifunctional’ structures experiment
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1() Figure 2. DS1 configuration. When the solar arrays are deployed, they span 11.5 m. ground engineering teams have begun learning the Conversion Engineering Conference, Honolulu, implications of incorporating these valuable new }11, July 28-August 1, 1997, paper 97539. technologies into their designs (and, of course, taking advantage of the capabilities of the 5. Rieciel, J. E., S. Bhaskaran, S. P. Synott, S. technologies in creating new designs). Thus, D. Desai, W. E. Bellman, P. J. Dumont, C. A. some of the benefits of the rapid infusion of these Halsell, D. Han, B. M. Kennedy, G. W. Null, new technologies into spaceflight have already W. M. Own Jr., R. W. Werner, and B. G. been realized; and any infomled user, seeking to Williams, “Navigation for the New Millennium: take advantage of the capabilities of these Autonomous Navigation for Deep Space 1,“ 12th advanced technologies, now would encounter International Symposium on Space Flight lower risk and cost by building upon the results of Dynamics, Darmstadt, Germany, 2-6 June 1997, DS 1‘s work to date. The actual execution of the paper 88. mission is expected to provide many more lessons of value for future spaceflight projects. 6. Beauchamp, P. M., R. H. Brown, C. F. Bruce, G-S. Chen, M. P. Chrisp, G. A. ~CKNOWLEDGMENTS Fraschetti, T. N. Krabach, S. W. Petrick, D. H. Rodgers, J. Rodriguez, S. L. Soil, A. H. The members of the DS 1 ground segment, Vaughan, L. A. Soderblom, B. R. Sandel, and R, mission, spacecraft, and technology teams are V. Yelle, “Pluto Integrated Camera Spectrometer gratefully acknowledged for their fine work in (PICS) Instrument,” Acm Asmomwica 35, developing the material on which this overview is Supplement 1995. based. 7. Bolton, S. J., D. T. Young, J. L. Burch, N. Some of the research described in this paper Eaker, J. E. Nordholt, H. O. Funsten, and D. J. was carried out by the Jet Propulsion Laboratory, McConlas, “Plasma Experiment for Planetary California Institute of Technology, under a Exploration (PEPE),” Space Technology and contract with the National Aeronautics and Space Applications International Forum 1997, January Administration. 26-30, 1997, Albuquerque, NM. REFERENCES 8. Rafferty, W., D. Rascoe, G. Fujikawa, and K. Perko, “Small Spacecraft Telecommunications for 1. Casani, E. Kane, “The New Millennium the New Millennium’s Technology Validation Program: An Overview,” Space Technology and Missions,” AIAA 34th Aerospace Science Applications International Forum 1997, Meetings, Reno NV, January 15-18, 1996, AIM Albuquerque, NM, January 26-30, 1997. 96-0700.
2. Rayman, Marc D. and David H. Lehman, 9. Wyatt, E. J., M. Foster, A. Schlutsmeyer, R. “NASA’s First New Millennium Deep-Space Sherwood, M. Sue (1997) “An Overview of the Technology Validation Flight,” Second IAA Beacon Monitor Operations Technology,” International Conference on Low-Cost Planetary International Symposium on AI, Robotics, and Missions, Laurel, MD, April 16-19, 1996, IAA- Automation in Space, Tokyo, Japan, July 14-16, L-0502. 1997. 3. Stocky, John F., Robert Vondra, Alan M. 10. Bernard, Douglas E. and Barney Pen, Sutton, “U.S. In-Space Electric Propulsion “Designed for Autonomy: Remote Agent for the Experiments,” AGARD Flight Vehicle Integration New Millennium Program,” International Panel Symposium, Cannes, France, October 3-6, Symposium on AI, Robotics, and Automation in 1994. Space, Tokyo, Japan, July 14-16, 1997.
4. Murphy, David M. and Douglas M. Allen, 11. Keast, C. L., R. Berger, J. A. Burns, J. M. “SCARLET Development, Fabrictition, and Knecht, R. R. Kunz, H. I. Liu, A. M. Soares, D. Testing for the Deep Space 1 Spacecraft,” C. Shaver, P. W. Wyatt, “A Sub-O.25pnl Fully Proceedings of the !ntersociety Energy Depleted SOI CMOS Process for Low Power
11 High Performance Applications,” 1997 Digest of Papers, Government Microcircuit Application Conference, pp. 333-336. 12. Carr, Gregory A. and Lauro A. France, “X2000 Power System Architecture,” Proceedings of the Iwersociety Energy Conversion Engineering Conference, Honolulu, HI, July 28-August 1, paper 97227.
13. Sercel, Joel, Brantley Hanks, William Boynton, Costa Cassapakis, Edward Crawley, Michael Curcio, Alok Das, William Hayden, David King, Lee Peterson, Suraj Rawal, Thomas Reddy, and Joseph Sovie, “Modular and Multifunctional Systems (MAMS) in the New Millennium Program,” AIAA 34th Aerospace Science Meetings, Reno NV, January 15-18, 1996, AIAA 96-0702.
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