SpinSat Mission Overview
Abstract : The SpinSat flight is a small satellite mission proposed by the Naval Research Laboratory and Digital Solid State Propulsion (DSSP) LLC to demonstrate and characterize the on-orbit performance of electrically controlled solid propellant technology in space. This is an enabling technology for the small satellite community that will allow small satellites to perform maneuvers. The mission consists of a spherical spacecraft fitted with Electrically Controlled Solid Propellant thrusters and retro-reflectors for satellite laser ranging (SLR). The spacecraft will be deployed from the International Space Station. This paper presents a mission overview and emphasis will be placed on the design, thruster design, optical layout, and unique SSA observation opportunities of the mission.
Multi-sensor Observations of the SpinSat Satellite
Abstract : The Naval Research Laboratory developed and launched the spherical SpinSat satellite to accomplish two primary goals: 1) study the performance of a new class of micro-thrusters, and 2) provide a calibrated drag experiment to characterize Earths upper atmosphere during the current period of relatively high solar activity. The 55.9 cm diameter aluminum sphere is equipped with a set of Electrically-Controlled Solid Propellant (ESP) thrusters, oriented to allow both translational and spin-up/spin-down maneuvers. To facilitate remote observations of the satellites spin rate, the spheres exterior features a reflectance pattern much like that of a beach-ball, a distributed sequence of retro-reflectors, as well as an ensemble of eight light-emitting diodes (LEDs) arranged along a meridian (i.e., a line of longitude) which can be turned on for brief periods. The Air Force Research Laboratory has conducted optical observations of SpinSat from several Advanced Maui Optical and Space Surveillance (AMOS) observatory sensors. The observational goals include: 1) obtaining time-resolved, multi-band measurements of the satellite actively firing its micro-thrusters, 2) characterizing the detectability and spatial/temporal morphology of the ESP thruster plumes, 3) measuring the spin rate of the satellite with the LEDs turned on, ideally before and after a spin rate adjustment maneuver, and 4) measuring the spin rate of the satellite in its completely inactive mode, using only passive observations of reflected light and/or thermal emissions.
Using laser radar polarization signatures for determining properties of a spinning sphere
This paper describes initial results on the use of a laser radar (LADAR)system to measure the rotational properties of a spinning sphere coated with two different surface materials. Numerical simulations were carried out using the Time-Domain Analysis Simulation for Advanced Tracking (TASAT) toolkit and a specialized laser ranging module included within the toolkit. Assuming some of the surface materials on the sphere's surface depolarize the incident radiation from the laser, the rotational properties of the object can be deduced. Futhermore, polarization properties of materials can enhance the ability to extract information about the sphere's rotational rate and relative orientation in the case where speckle noise and tracking jitter is significant. Future work will involve the creation of a large database of simulated return signatures for many orientations and rotation rates. The database will be correlated against actual LADAR measurements in order to determine the rotational and orientation properties of spinning objects in low earth orbit.