Patrick Seitzer, University of Michigan; Justin H. Schachter, University of Michigan; Matthew Szczerba, University of Michigan; Daniel Gu, University of Michigan; Anny Lin, University of Michigan; Chris H. Lee, University of Michigan; James W. Cutler, University of Michigan; Peter D. Washabaugh, University of Michigan; Nathan Estell, University of Michigan; George Bryja, University of Michigan
Keywords: LEO, CUBESAT, LED, LEDsat, orbit determination, optical tracking
Abstract:
On the night of May 10, 2018, the University of Michigan successfully flew and optically tracked a high-altitude balloon mission equipped with light emitting diodes (LEDs) as a precursor and prototype mission for using LEDs on CubeSats Project LEDSAT. We present the results from this flight, which was actively tracked at a range of 54 km using an 85-mm aperture telescope and CMOS detector.
The rapidly growing population of satellites in low Earth orbit (LEO) means that new techniques will be needed for tracking, orbit determination, and spacecraft identification. Project LEDSAT will demonstrate the use of LEDs on LEO satellites combined with existing ground based optical telescopes to augment current LEO tracking methods. It is an international effort to evaluate the use of LEDs for position determination, attitude determination, and telemetry. In the case of simultaneous launches of large numbers of CubeSats, LEDs could aid in satellite identification quickly after deployment. The plan is for the University of Michigan and the University of Rome “La Sapienza” to launch separate CubeSats each equipped with LEDs for these purposes. For LEO satellites, the presence of LEDs means that the satellite can be tracked even during eclipse periods, increasing the number and duration of passes that the satellite can be observed.
The balloon mission was conducted by MXL, a research laboratory of the University of Michigan Aerospace Engineering Department. MXL has flown 7 CubeSats and 30 high- altitude balloon flights as technology demonstrations and science missions in collaboration with organizations such as NASA-JPL, NSF and SRI International. Optical tracking was conducted by the Department of Astronomy of the University of Michigan, which has telescopes in southeastern Michigan to optically track the balloon payload and has telescopes in both Arizona and Chile for satellite tracking.
The balloon flight was conducted at nighttime to simulate tracking a CubeSat during eclipse. The payload consisted of two orthogonal LED panels on the walls of a 3D printed CubeSat structure. Each panel consisted of 15 COTS high power LEDs (1 Watt rated) and driver circuitry. The panels were operated out phase of one another and flashed unique signals so they could be differentiated in the captured images providing both attitude and position information. The signals were timed so that a ground station would see the flashes of light as point sources, simulating stars, which permitted accurate photometry and astrometry. Also on-board the payload was a real-time clock, a 3-axis accelerometer, a 3-axis gyroscope, a 3-axis magnetometer, a GPS receiver, and an APRS GPS-position transmitter. These sensors were included in order to log the orientation and transmit position of the payload during the flight.
The optical ground station used in the mission was the Angell Hall Observatory located in Ann Arbor, MI and consisted of an 85-mm aperture telescope mounted on a 0.4-m telescope controlled by an internet connected computer system. A custom-built tracking algorithm used the APRS transmitted position of the balloon payload to point the telescopes in real-time, so images could be captured on a CMOS camera on the 85-mm telescope. Active tracking was performed successfully with detection of the balloon LEDs at distances greater than 50 km using the small telescope. Individual images of the balloon LEDs demonstrated a signal-to-noise ratio (SNR) of greater than 20 with a city background proving that LED based optical tracking in an eclipse period is feasible.
Date of Conference: September 11-14, 2018
Track: Poster