Exploring the Mysteries of the Cosmos on the MOST Microsatellite Mission Dr. Simon Grocott Dr. Robert E Zee Dr. Jaymie Matthews Dynacon Inc UTIAS SFL UBC 13 August 2003
Outline MOST (Microvariability and Oscillations of Stars) Microsatellite developed under CSA Space Science Small payloads program MOST Science MOST Satellite MOST Status
MOST Science: Stellar Seismology Sound waves caused by turbulence in the Sun s outer layers cause it to ring like a giant gaseous bell The ringing makes the Sun oscillate in brightness at a level of a few ppm We can use the surface vibrations to seismically probe the hidden interior
Primary Targets Sun- like stars metal- poor subdwarfs Giant exoplanets orbiting other stars 51 Peg b 51 Peg a
MOST brightness data
Exosolar Planet Light Intensity Simulation The MOST Science Team may be the first humans to see the reflected light from a planet outside our Solar System
Systems Overview Spacecraft Modes Safe Hold Mode has no ACS, only Rx and HKC powered, power positive because all faces have solar panels Detumble mode uses magnetorquers to slow tip off rates Pointing modes have 3-axis inertial ACS Long duration (up to 40 days) ultrastable (25 arcsec ) pointing requirement Dawn-Dusk Sun Synchronous orbit at 800 km provides ~27 degree CVZ and short 12 week eclipse season
Periscope Assembly Telescope Optics CCD Cameras 53 kg satellite, 60x60x30 cm approx. 15-cm aperture, visible light telescope. Mechanical backbone consists of stacks of electronics trays, one for each major subsystem. Aluminum structure and panels. Mainly passive thermal control. Battery heaters CCD focal plane trim heaters Tray Stack of Electronics Excess power generation shunted to end trays
Periscope Mirror Magnetometers Star Facing Side Telescope Aperture Sun Facing Side Sun Sensors Telescope Bay Passive Radiator (not shown) Launcher Attach Actuated Door (not shown) Aux Solar Panel Quadrifilar Antennas (under hats) Main Solar Arrays
Launch: Access to Space Launch 30 June 2003 on Rockot Launch Vehicle Initially planned for launch in Nov 2001 as secondary to Radarsat II Radarsat II launch now Aug 2005 Change of launch vehicle led to redesign of major structural components delayed program by about 1 year
Commissioning First pass over University of Toronto groundstation approximately 5 hours after spacecraft separation Contacted spacecraft downloaded realtime telemetry spacecraft was in excellent shape, batteries fully charged all systems operating normally Scheduled two month process of commissioning main computer ACS equipment (detumble and coarse pointing) Instrument and star tracker Fine pointing
Detumble 50 40 Magnetic field measurement (microtesla) 30 20 10 0-10 -20-30 -40-3000 -2000-1000 0 1000 2000 3000 4000 5000 6000 time(sec) Detumbled from 3 deg/sec to <0.1 deg/sec in <6000 sec
Pointing AlphaEst; Pointing State (cyan); SunfValid (magenta) 6 4 2 alphaest (deg) 0-2 -4-6 -8 0 20 40 60 80 100 120 140 160 180 200 UTC time (seconds) Pointing maneuver, attitude determination, slew, stabilization
First Light 29 July 2003 opened door that covers telescope aperture took first star image a faint star in the constellation Capricorn.
Conclusion What makes MOST successful at a low cost Clear and narrowly focused science goals Low cost microsatellite approach utilizing commercial technologies High accuracy Attitude Control System (ACS) necessary for science not seen before on microsatellites Focused, Integrated approach. Scientists and engineers working closely together