Lessons Learned From the Clementine Mission
The Clementine mission carried out by the Department of Defense's (DOD's) Ballistic Missile Defense Organization (BMDO) was quite unusual by recent NASA standards: the mission objectives were primarily technological with secondary but significant science goals; the mission's definition and development were completed on a speedy schedule toward a fixed launch date; the project team was small, as was the BMDO program management staff; and fiscal resources were limited, but the team had access to a large pool of newly developed spacecraft technologies and in-place contracts. Clementine occurred during the period when NASA was shifting its program toward "smaller, cheaper, faster" missions, such as the Discovery and MidEx programs, that are intended to have many of the characteristics of the BMDO mission. The performance of Clementine is, therefore, directly relevant to the prospects of these new NASA programs.
THE ROLE OF SMALL MISSIONS
Even though NASA has flown "Clementine-style" spacecraft in the
past and has periodically made concerted attempts to establish lines
of small planetary missions prior to the current Discovery program,1
the scientific potential of such missions remains a controversial
topic. While many claims have been advanced for small missions,
it is impossible to ignore the successes of "large" programs such
as Viking and Voyager. Moreover, it is difficult, if not impossible,
to estimate how many "small" missions would have been required to
produce the same yield of scientific results and at what cumulative
cost, including the load on the Deep Space Network and other operational
expenses. Past COMPLEX reports have some bearing on these issues.
The committee's 1994 report, An
Integrated Strategy for the Planetary Sciences: 1995-2010,
explains that a responsive planetary exploration program demands
a mix of mission sizes ranging from comprehensive missions with
multiple objectives (such as Galileo and Cassini) to small missions
with highly constrained scientific objectives.2
At the same time The Role of Small Missions
in Planetary and Lunar Exploration concluded that a series
of small missions present "the planetary science community with
the opportunity to expand the scope of its activities and to develop
the potential and inventiveness of its members in ways not possible
within the confines of large, traditional programs."3
Thus, COMPLEX does not believe that there is a simple, all-purpose
conclusion to the small-versus-large issue; rather, the potential
scientific return per dollar spent is something to be determined
in the selection of individual missions and not by an abstract analysis
of large versus small.
No study of the Clementine mission is complete without a note about the quite different "cultures" operating within DOD and NASA. A full analysis of these differences was beyond the scope of this study. Several differences, however, were immediately obvious to COMPLEX. These include:
The greater resources available overall to DOD versus NASA;
The underlying sense of urgency surrounding military projects contrasted with the more leisurely pace of civil programs;
Less involvement by Congress, and reduced micromanagement on the part of DOD leadership in the day-to-day aspects of the program; and
A narrower, more focused, task-force-like management style that differs greatly from the broad, participatory approach more familiar to members of the scientific community associated with NASA's missions.
An issue related to the different cultures of DOD and NASA is their potential rivalry. Although the size and scope of DOD's space activities
match or exceed those of NASA's, there has been little direct competition between the two programs in the past. Recent concerns about the hazards posed by near-Earth objects and the U.S. Air Force's reported interest in assuming the role of lead agency for planetary defense could exacerbate potential rivalries. With proper management, however, such a rivalry could be constructive.
CLEMENTINE AND ITS GOALS
The Clementine mission's primary goals were to space-qualify advanced, lightweight imaging and multispectral cameras (as well as component technologies) and to test autonomous operation for the next generation of DOD spacecraft. Shortly after the idea for this mission was conceived, secondary objectives—to perform a 2-month global mapping survey of the Moon and a flyby of the near-Earth asteroid, 1620 Geographos—were added. The specific science goals for Clementine were dictated by the capability of the spacecraft and the availability of instruments that matched this capability, rather than by well-established priorities for lunar science.4,5
To meet BMDO's goals, Clementine implemented a streamlined management style that included a rapid design and development program, with an approval-to-launch time line of 22 months. Of particular note was an innovative approach to mission operations and data handling, characterized by the intimate involvement of the science team in the day-to-day, indeed hour-to-hour, operation and planning of the science observations. The spacecraft was designed, built, tested, launched, and operated for a reported cost of about $80 million ($9 million for spacecraft systems, $8 million for instruments, $38 million for spacecraft integration, $20 million for the launch vehicle, and $5 million for operations; see Table 1.1).6
TABLE 1.1 Clementine Budget: Projected and Actual Cost Estimates (in FY 1992 $) Through May 31, 1994, for Various Aspects of the Clementine Mission
|Attitude control System
|Reaction control system
|Electrical power subsystem
|Total payload cost
|Total mission cost
|NOTE: Although COMPLEX did no detailed analyses to verify any of these figures, none of the data seems unreasonable.
SOURCE: As supplied to COMPLEX by Paul Regeon, Clementine's program manager at the Naval Research Laboratory.
The spacecraft, whose characteristics are summarized in Box 1.1, was launched on January 25, 1994 (by a refurbished Titan IIG ICBM), and, using a phasing-orbit transfer trajectory, was inserted into a polar orbit on February 19, 1994. It orbited the Moon for 71 days, during which it acquired almost 2 million digital images of the Moon at visible and infrared wavelengths, improved the determination of the Moon's gravitational field, and, through laser ranging, accurately measured the global lunar topography. The asteroid flyby and its accompanying test of autonomous navigation were aborted because, following a software error, the attitude control gas was entirely depleted.
|Box 1.1 Characteristics of the Clementine Spacecraft
— Space vehicle (launch adapter, kick motor, interstage, and spacecraft): 1,691 kg
— Spacecraft (dry weight): 235 kg
— 3-Axis stabilized via reaction wheels
— Ring laser gyro and interferometric fiber-optic gyro inertial measurment units
— Solid rocket motor for lunar injection
— N2O4/MMH* for propulsion
— N2H4 for attitude control system
— 2.0-gigabyte DRAM,* solid-state data recorder
— Parallel processor architecture
— Mil-Std-1750A (1.7 MIPS*) for safe mode, attitude control system, and housekeeping
— R3081 (18 MIPS) for image processing, attitude control system, and autonomous processing
— Gimbaled (single-axis) GaAs/Ge* solar array (2.3 m2, 460 W at 30 V D.C.)
— 15 amp-hour NiH2 common pressure vessel battery
— Deep-space network compatible transponder without encryption
— 128-kilobits per second (kb/s) downlink (max); 1-kb/s uplink
*Abbreviations and acronyms are defined in the glossary.
SOURCE: As reported by Pedro Rustan, Clementine program manager, at the Clementine Engineering and Technology Workshop, July 1994.
The first half of the remainder of this report provides a preliminary assessment of the science accomplishments of Clementine; this assessment is based on a series of published papers7 as well as interviews with team members and other lunar researchers. The report then lists some of the lessons that the space science community might learn from Clementine's mode of operation, which had more in common with the Discovery and MidEx approach than traditional NASA missions.
1. See, for example, Space Studies Board, National Research Council, The Role of Small Missions in Planetary and Lunar Exploration, National Academy Press, Washington, D.C., 1995, pages 5-9.
2. Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995-2010, National Academy Press, Washington, D.C., 1994, page 186.
3. Space Studies Board, National Research Council, The Role of Small Missions in Planetary and Lunar Exploration, National Academy Press, Washington, D.C., 1995, page 2.
4. Lunar Exploration Science Working Group, A Planetary Science Strategy for the Moon, JSC-25920, NASA, Solar System Exploration Division, Houston, Texas, 1992.
5. Space Studies Board, 1990 Update to Strategy for Exploration of the Inner Planets, National Academy Press, Washington, D.C., 1990.
6. Paul Regeon, "Clementine: Overview and Lessons Learned," presentation to COMPLEX, October, 1994.
7. S. Nozette et al. "The Clementine Mission to the Moon: Scientific Overview," Science 266:1835-1839, 1994.M.T. Zuber et al. "The Shape and Internal Structure of the Moon from the Clementine Mission," Science 266:1839, 1994.
C.M. Pieters et al. "A Sharper View of Impact Craters from Clementine Data," Science 266:1844, 1994.
P.D. Spudis, R.A. Reisse, and J.J. Gillis, "Ancient Multiring Basins on the Moon Revealed by Clementine Laser Altimetry," Science 266:1848, 1994.
E.M. Shoemaker, M.S. Robinson, and E.M. Eliason, "The South Pole Region of the Moon as Seen by Clementine," Science 266:1851, 1994.
P.G. Lucey et al. "Topographic-Compositional Units on the Moon and the Early A.S. McEwen et al. "Clementine Observations of the Aristarchus Region of the Moon," Science 266:1858, 1994.
P.G. Lucey, G.J. Taylor, and E. Malaret, "Abundance and Distribution of Iron on the Moon," Science 268:1150, 1995.
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