December's STS-116 launch includes three amateur satellites

Space Shuttle Discovery is scheduled for launch on December 7 at 9:35 PM EST (UTC-5).

During the 12-day mission and three spacewalks, the crew will work closely with flight controllers at NASA's Johnson
Space Center, Houston, to install a new segment of the station's girder-like truss and activate the station's permanent, complex power and cooling systems.

The Shuttle will also carry to orbit three new satellites, RAFT-1, MARSCOM and ANDE, designed, built, and tested by the Midshipmen of the US Naval Academy's Satellite Laboratory in Annapolis, Maryland.

The primary mission of the RAFT satellite is tied to the calibration of the US Navy Space Surveillance Radar which is the primary source of ALL satellite tracking data for ALL spacecraft in the USA. Data from this radar is what helps generate the Keplarian Elements used by all Amateur Satellites operators.

The secondary mission of RAFT and MARScom are to provide packet digital communications relay for mobile units to transmit their GPS coordinates and messages via the satellites. This is a continuation of the PCsat, PCSAT2 and ARISS missions.

The downlink is received by a global system of volunteer ground stations that feed the http://pcsat.aprs.org live web page.

The primary limitation on single channel LEO satellite communications is the congestion on the uplink. The RAFT Packet-to-Voice transponder solves this problem by compressing the uplink into a single 1 second burst per station, and then expanding it to voice for the FM downlink.
This way, students with nothing but a scanner receiver can hear all of the downlink communications (voice) yet the uplinking stations have a very low probabilty of collision due to the short duration of the uplink. A voice synthesizer converts the packet to voice.

ANDE was developed by the Naval Research labs as an "Atmospheric Neutral Density Experiment" to measure the decay from orbit of a perfectly spherical 18" ball. Hearing that it was empty, the Naval Academy under the mentoring of Bob Bruninga, WB4APR, proposed an amateur radio transponder for the inside.

There can be no external antennas and no solar panels or anything that would disturb the aerodynamic performance of the very smooth sphere. The spherical satellite is split in half with an insulator and uses the space frame as the antenna for the 2 meter system. There are 112 Lithinum primary "D" cells inside the sphere to power it for a year.

To keep the current drain to a minimum, the ANDE comms payload sleeps 90% of the time, only waking up once every 16 seconds to listen for packets. Hearing none, it goes back to sleep to convserve power. If packets are heard, then it remains awake and serves as an APRS packet digipeater until 1 minute after the last packet. In addition, ANDE has a
voice synthesizer and can speak packets addressed to it.

The telemetry from the satellite will be of a similar form to that of PCSAT and PCSAT2 and will be distributed by the APRS-IS network. Dave, G4DPZ has been working on the telemetry web site. Details of the URL will be published after launch.

The RAFT-1 and ANDE satellite downlinks will be 145.825 MHz. The MARS frequencies used by MARSCOM are on Navy-Marine Corps MARS frequencies.

For full technical details please refer to:
http://www.ew.usna.edu/%7Ebruninga/ande-raft-ops.html

Bob, WB4APR,
US Naval Academy Satellite Laboratory

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