Store-and-Dump Telemetry

Spitzer is also able to maximize its efficiency by utilizing a "store-and-dump" method of transferring data from the telescope back to Earth.

When the scientific observations are taken, Spitzer stores up the data instead of transmitting it all back to Earth immediately. Spitzer's high-gain antenna is fixed to point in a single direction, so the observatory interrupts its science program twice a day to re-point the antenna towards the Earth and downlink all of the data.

The average data transfer rate is 85 kilobits per second (kbps). In case Spitzer misses a telemetry pass for some reason, there is 8 gigabits of onboard data storage, which prevents data being overwritten before it can be downlinked to the ground. Communications with Spitzer are all handled through NASA's Deep Space Network, with roughly one-hour communication windows scheduled approximately every 12-24 hours.

This method ensures that Spitzer spends as little time as possible transferring data between the observatory and the ground, and instead spends the vast majority of its precious lifetime conducting scientific observations. It is estimated that Spitzer will make 100,000 or more observations during its 5.5-year lifetime.

New observing schedules are sent to the telescope every week, although it is possible to interrupt the schedule and uplink new instructions more frequently if an urgent observation request is triggered by one of the astronomers using Spitzer (called a "Target of Opportunity").