Small Spacecraft Conceptual Design for a Lunar Polar Mapping
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I I SMALL SPACECRAFT' CONCEPTUAL DESIGN FOR A LUNAR POLAR I MAPPING/EDUCATIONAL SPACECRAFT' Peter A. Warren and Michel E. Loucks Colorado Space Grant Consortium University of Colorado I Boulder, Colorado I Abstract Educator will also provide valuable data on the lunar gravity field simply from its own The Lunar Educator is a Phase A mission tracking. The lunar educator can also act as a I definition and development activity being beacon for a second sub orbiting spacecraft to undertaken by the University of Colorado's provide gravity modeling information for the Space Grant Consortium. The scientific far side of the moon. objectives of the mission are to provide I greater than 50 meter resolution visual images The educational aspects of this mission of the Lunar polar regions from various extend from the current design effort through lighting angles in order to discover the construction and operations phase into the I permanently shadowed craters, and, if data reduction and analysis work. The spacecraft lifetime allows, to digitally map the current spacecraft design was developed entire lunar surface. Of equal importance is entirely by graduate and undergraduate I the program's educational objective to use students at the university of Colorado. The this mission as a platform to educate and fidelity of the design effort was achieved by excite people of all ages in math, science, using a mentor system in which the students engineering, and space exploration. The drew heavily from the experience of academic I Lunar Educator program intends to and industry professionals to understand the accomplish these goals with a simple, low real issues behind the design and construction cost spacecraft built and operated entirely by of spacecraft systems. Future hardware I undergraduate and graduate level students. development and construction efforts will be undertaken in the same fashion as Space Introduction Grant's successful sounding rocket and Get -Away-Special programs. The spacecraft I The Lunar Educator is a scientific and will be operated out of the University of educational mission being undertaken by the Colorado much as the Solar Mesosphere university of Colorado. It is an on-going Explorer (SME) was with the help of I effort that began in January of 1992 and is additional universities and educational currently in a phase AlB design mode in institutions around the globe. The data which a conceptual design has been acquired by this mission will be distributed I developed and some flight hardware has been by a variety of means to K-12 level to allow selected. The scientific objectives of the teachers to use this data to educate their mission are to provide comprehensive visual students in science, math and engineering. images of both lunar poles at a pixel I resolution of greater than 50m. Once the Design Approach poles are completely mapped at several different solar lighting angles, the imaging The design of the Lunar Educator spacecraft I system will then be used to map as much of and mission has been driven by four the lunar surface as spacecraft lifetime will requirements that derive from its dual allow. The polar Images will aid in the scientific and educational nature; I search for lunar ice and the lunar surface maps will contribute to the body of I knowledge of planetary science. The Lunar I I I 1) The spacecraft must be simple enough These four requirements can be summed up for students to design, build, and as Simple, Good, Cheap, and Fast. The operate. combination of these requirements results in a quickly developed, simple mission that I 2) The mission must be scientifically provides a modest science return for a low worthwhile. cost. The four different requirements complement each other quite well. The short I 3) The program cost must be low enough to development time reduces the total overhead be managed within the university costs. The low level of complexity reduces system. both the development cost and time. The low I cost allows the relatively simple science to 4) The spacecraft development time must be have as much "bang for the buck" as larger, within a student's career. more complex, and expensive missions. And the good science in a short time brings in the I The first requirement derives from the interest of the planetary exploration . educational aspects of the mission. The community as it provides an early precursor primary educational thrust of this mission is to future lunar exploration. I to get the next generation. of engineers and scientists hands-on experience in the realities These seemingly contradictory requirements of designing, building and flying a scientific are met by employing design philosophies I space mission. Making the program too large that are a departure from standard scientific or complex for a student organization would mission practices. These departures can be eliminate this educational benefit summed up as follows; I The second requirement is to provide a real 1) Use surplus hardware wherever possible benefit to the planetary science community: even if it affects the overall mission plan. In order for the program to appeal to the I students as well as the scientists it cannot be 2) Use only existing designs and simply a flag-waving endeavor, real science technology. must be performed. 3) Do not build anything specialized unless I The third requirement is a concession to the absolutely necessary. pragmatics of funding and program management. If a program gets too large and 4) Do not add to the basic science I costs too much, greater restrictions and capabilities ofthe mission unless there are overhead costs are placed on the program minimal design and cost impacts. management I The specific impacts of this design Additionally, the required simplicity of the philosophy to this mission will be described program dictates a relatively simple science in the "Design History" and "Current mission. To keep the dollars to science ratio Baseline Design" sections. The generalized I on a par with larger missions, the cost must impacts are quite clear. The resulting be correspondingly modest. The funding spacecraft and mission are not optimized for level anticipated for this effort is under $10 high performance or to serve a broad I million. scientific community. Instead, the mission is optimized for cost and simplicity. Using The fourth requirement enables continuity surplus hardware and existing technology I through out the design and construction results in spacecraft systems that are over process. Previous experience at the Colorado built for the specific mission. However, by Space Grant College has shown that students using surplus and off-the-shelf hardware, learn a great deal more if they are able to long procurement cycles are avoided, thus I watch their design efforts go through the cutting development time and cost. growing pains of becoming a reality. I 2 I I I interplanetary volatiles has been debated for The spacecraft and scientific mission that some time. Since the moon's axis is nearly result from these design requirements and perpendicular to the ecliptic plane, it is philosophy is a quick, simple mission that possible that the rim of a crater on the north I provides a modest science return for a or south pole could block any sunlight from minimal cost. The education and experience ever reaching certain areas internal to the that the students receive while designing, crater (see Figure 1). I constructing and operating the spacecraft is unparalleled. Incident Sunlight I Science The science the Lunar Educator performs is Shadow Area separated into two basic categories, visual I imaging and gravity model refinement. The visual imaging is accomplished using a high Figure 1. Permanently Shadowed Polar resolution Charged Coupled Device (CCD) Crater I camera that produces gray scale images of the lunar surface. Both poles of the moon will These areas would be extremely cold (_3° be completely mapped from different sun Kelvin) and may act as a trap for volatile angles to provide detailed information on materials such as water, carbon dioxide, etc. I these unexplored regions and to identify Such frozen "lakes" of material would be of those crater areas that are permanently tremendous value both as a selenological shadowed. The discovery of permanently record akin to Earth's polar ice caps and as a I shadowed craters would be a ftrst step in the valuable resource for future lunar missions. search for lunar ice. The lunar gravity model would be much reftned simply by tracking a By imaging the lunar polar craters throughout I spacecraft in a lunar polar orbit. In addition, a complete cycle of sun angles, the Lunar the Lunar Educator will carry an Ultra Stable Educator program would be able to identify Oscillator (USa) to act as a beacon for a which craters were permanently shadowed, second spacecraft in a lower orbit for gravity thus paving the way for future moon I modeling of the far side of the moon. missions. Time-lapse photography of these regions would be accomplished from a Lunar Imaging "frozen" orbit that stays fixed as the moon I rotates underneath it, thus providing different The lunar poles are of interest for two lighting angles over a long time periods. reasons, first because they are the least This orbit is described in detail in the I researched area of the moon and secondly following sections. because of the possibility of discovering frozen volatiles such as water or carbon Lunar images are obtained by a 1024 by 1024 dioxide (Refs. 1-2). The lunar poles were pixel array looking through a 10 cm diameter I not mapped in detail during the initial race to Catoptic telescope. Each image is 51.2 km the moon since they did not contain viable by 51.2 km, with a pixel resolution of 50 landing sites.