Innovations: Store-and-Dump Telemetry

NASA/JPL

Employing onboard, solid-state memory and lossless data compression software, Spitzer utilizes a store-and-dump philosophy of data transfer to the ground. The high-gain antenna on the back end of Spitzer is fixed, so the spacecraft will interrupt its science program once or twice a day to re-point the Observatory to Earth and downlink the data. Telemetry will be provided through NASA's Deep Space Network, with nominal one-hour communication windows scheduled every 12 to 24 hours.

New observing schedules will typically be uplinked to the spacecraft on a weekly basis, although the telemetry design offers the opportunity for more frequent contact (especially early in the mission). The average data acquisition rate is 85 kilobits per second (kbps). Onboard storage capability of 8 Gigabits permits ground operations to downlink a full day of science in the event of a missed telemetry pass.

Taken together, the choice of orbit and the telemetry requirements suggest that Spitzer will spend the vast majority of its precious lifetime conducting valuable scientific observations. It is estimated that Spitzer will make 100,000 or more observations during its predicted five-year life.