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Lunar IceCube is a NASA nanosatellite mission designed to prospect, locate, and measure volumes and composition of water ice deposits and other volatiles on the Moon in support of future exploitation by robots and human explorers. Lunar IceCube is one of several public -private partnerships selected under NASA's Next Space Technologies for Exploration Partnerships Broad Agency Announcement for the development of advanced exploration systems. Among the first small satellites planned to explore deep space, Lunar IceCube, along with the 12 other Exploration Mission One (EM -1) missions will help lay a foundation for future small-scale planetary missions. In addition to providing useful scientific data, Lunar IceCube will help inform NASA's strategy for sending humans farther into the solar system.

Here we describe the Primitive Object Volatile Explorer (PrOVE), a smallsat mission concept to study the surface structure and volatile inventory of comets in their perihelion passage phase when volatile activity is near peak. CubeSat infrastructure imposes limits on propulsion systems, which are compounded by sensitivity to the spacecraft disposal state from the launch platform and potential launch delays. We propose circumventing launch platform complications by using waypoints in space to park a deep space SmallSat or CubeSat while awaiting the opportunity to enter a trajectory to flyby a suitable target. In our Planetary Science Deep Space SmallSat Studies (PSDS3) project, we investigated scientific goals, waypoint options, potential concept of operations (ConOps) for periodic and new comets, spacecraft bus infrastructure requirements, launch platforms, and mission operations and phases. Our payload would include two low-risk instruments: a visible image (VisCAM) for 5-10 m resolution surface maps; and a highly versatile multispectral Comet CAMera (ComCAM) will measure 1) H2O, CO2, CO, and organics non-thermal fluorescence signatures in the 2-5 μm MWIR, and 2) 7-10 and 8-14 μm thermal (LWIR) emission. This payload would return unique data not obtainable from ground-based telescopes and complement data from Earth-orbiting observatories. Thus, the PrOVE mission would (1) acquire visible surface maps, (2) investigate chemical heterogeneity of a comet nucleus by quantifying volatile species abundance and changes with solar insolation, (3) map the spatial distribution of volatiles and determine any variations, and (4) determine the frequency and distribution of outbursts.

A mobile weighing system was designed in 1994 to weigh small lysimeters to measure water use by shallow-rooted crops. Using a reconditioned pesticide sprayer, a hoist, and a weighmeter, small lysimeters were weighed in the 1995, 1996, and 1997 growing seasons. The lysimeters were constructed of 4.8-mm hot-rolled steel and were 0.91 x 1.02 x 0.61 m in size with an internal area of 0.929 m 2 . The weight of a lysimeter containing only moist soil was 1.110.27 kg. At the beginning of each season of use, several tests were conducted on the weighing system to determine if it was sensitive enough to give adequate results of crop water use. In 1995, tests were conducted on linearity, repeatability, thermal shift, and creep errors. The values were ±0.062 kg, ±0.12 kg, -0.007 kg/ ° C, and -0.242 kg, respectively. The terminal linearity was 0.082 kg (1996) and 0.043 kg (1997). The measurement uncertainty decreased as the number of lifts increased. The results showed that the system was capable of producing adequate results for determining crop water use.

This paper presents the general relative orbit dynamics equations and GPS orbit observational equations that have been developed for on-board control of spacecraft flying in formation. The approach to the implementation of the autonomous control for orbit acquisition maintenance of spacecraft formation using GPS code pseudo-ranges are presented. The orbit control of the Earth-Orbiter 1 (EO-1)/Landsat 7 system has been designed, using the discrete-time linear optimal output feedback control. For the actuator of the on/off type reaction jets, the implementation problem of the pulse-amplitude modulation is also studied. Simulation results of autonomous orbit control and maintenance, for 3D initial orbit error, using optimal output feedback control are shown. These simulation results certified the feasibility of the implementation of the autonomous maintenance control for EO-1/Landsat 7 formation flying by means of the discrete-time linear optimal output feedback control.