ACE

Telecommunications Description

Onboard telemetry data storage is 1.3 Gbit which allows storage of 52 hours of data acquired continuously at 6.944 kbps. There are three modes of telemetry communnication with the spacecraft. The primary mode is at 88 kbps and includes two virtual channels, one composed of a real time data stream (RTDS) and the other of playback from the recorded data stream (RCDS) from the onboard recorders. The second mode is a 8 kbps data rate which does not include RCDS playback. There is also a slow mode of 418 bps for spacecraft housekeeping and status data. Telemetry data will be handled by the DSN on the S-band for daily contacts of about three hours at a forward rate of 1 kpbps and return rate of 88 kbps. The annual volume of telemetry data processed by GISE and transmitted to the Ace Science Center (ASC) will be about 220 Gbits. Telemetry data transmission to the ASC will be done via NSI with the TCP/IP protocol for the real-time data stream (RTDS) and via 4-mm tapes for the recorded data stream (RCDS). GISE will send integrated command files (based on ASC coordination of experiment inputs) to the spacecraft via the DSN uplink.