| SPACECRAFT | |
| Small Explorer (SMEX) Computer System: | 80386/80387 Processor, 300 Mbps Solid State Recorder, 1553 Data Bus |
| Communication System: | S-band transponder, 2 Kbps uplink, 2.25 Mbps downlink |
| Attitude Control System: | Analog acquisition using an 8085 processor, Science mode uses instrument provided guide telescope as fine error sensor for spacecraft and image motion compensation, pointing accuracy < 5 arc seconds |
| Small Explorer (SMEX) Power Electronics: | Direct energy transfer, partial array shunting with no shunt resistors |
| Mechanical Structure: | Semi monocogue, thrust tube design using riveted Aluminum |
| Battery: | 9 Ah "Super" Nickel Cadmium |
| Solar Arrays: | Gallium Arsenide Solar Cells, some multi-junction test cells |
| Actuators: | Four reaction wheels, three magnetic torque rods |
| Sensors: | Three two-axis gyros, one digital Sun sensor, six coarse Sun sensors, one three-axis magnetometer, instrument guide telescope |
| INSTRUMENT | |
| Telescope: | 30 cm diameter x 160 cm length, 8.66 m focal length Cassegrain |
| Detector: | 1024 x 1024 Lumigen coated CCD |
| Optics: | Super-polished mirrors individually coated in four quadrants. Active secondary with image stabilization |
| Thermal: | Detectors passively cooled to -65°C |
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| TRACE mated with Pegasus |
TRACE | TRACE |
TRACE Launch
TRACE arrived at Vandenberg, AFB in February 1998 only to experience the harsh realities of Mother Nature. The winter of 1998 brought with it the pounding rain storms of El Nino, forcing the abrupt evacuation of the TRACE spacecraft and team to high ground. Fortunately the team and spacecraft survived and encountered only minor delays in testing and integration to the Pegasus rocket. TRACE was successfully launched on April 2, 1998 in Universal Time. TRACE's arrival to orbit couldn't have been smoother. After a missed initial acquisition at the McMurdo ground station in Antarctica, TRACE telemetry was successfully acquired an hour and a half into the mission. The Mission Operations Control team verified that the solar arrays had deployed and the ACS system was pointing the spacecraft at the Sun. In the following couple of days, controllers verified the health of an exciting new solar telescope.
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| TRACE | Roll out to hot pad |
Mated to L-1011 |
Drop from L-1011 |
Mission Operations
Operations to date have been relatively smooth and uneventful. As of May, 1999 TRACE has taken over 1.5 million images of various solar features in coordination with SOHO and other solar observatories around the world. Detector degradation has been unexpectedly light providing scientists with the hope of several more years of good seeing. TRACE experienced its first "eclipse season", when TRACE went through a day/night cycle every orbit rather than seeing the Sun 100% of the time, November 1998 through February 1999. Fortunately, we are able to say that "TRACE is power fat" meaning specifically its battery performance has exceeded requirements by 80 Watts. Consequently, the Mission Operations Team was able to leave the instrument powered on throughout eclipse season, providing the solar community with full disk mosaic images while the SOHO spacecraft was experiencing problems. TRACE even survived the Leonids Meteor Storm of November 1998. During this event, mission controllers successfully pointed the telescope and the very thin entrance filters away from the micrometeoroids and dust contained in this 33-year periodic event. With luck, this smooth sailing will continue into mission years two and three.
