Communication System One of Starshine 3 primary objectives is to involve more school children in radio science. As part of this mission, science data from experimental solar cells mounted on the surface of the satellite will be downlinked in a manner that will allow schools and radio amateurs to participate in collecting the data. For this reason, the downlink has been designed for compatibility with standard amateur satellite radio ground stations. It is also compatible with Kenwood THD-7 hand-held radio terminals. The THD-7 radios contain built-in AX.25 Terminal Node Controllers (TNCs) and RS-232 ports. Consequently, you can receive Starshine 3 downlink signals directly, for recording on a standard laptop or desktop computer. Schools that purchase THD-7 or similar radios will be able to receive the Starshine 3 signals with their identifying "STRSHN3 N7YTK" data header very simply. We ask that you forward your received packets as soon as possible to a special radio data collection web site that has been created for us by Michael Tolchard at http://dinepath.com/starshine/. The Starshine 3 Communications System downlink uses 9600 bps Frequency-Shift Keyed (FSK) signals at 145.825 MHz. Downlink transmissions will initially occur at two-minute intervals. (The interval will be shortened to every thirty seconds, if the surface-mounted solar cells charge the on-board batteries satisfactorily.) The Starshine 3 Communication System parameters are given below in Table I. Table I: Starshine 3 Communications System Parameters Characteristic Type/Value 1. Center Frequency 145.825 MHz 2. Data Rate 9600 bps 3. Modulation Narrowband FSK 4. Deviation +/- 3 KHz 5. Baseband encoding Differentially-encoded Non-Return to Zero (NRZI) 6. Scrambling G3RUH 7. Protocol AX.25 packet radio -- APRS packet compatible. 8. Uplink/Downlink Multiplexing: Half Duplex 9. RF Transmit Power 1.25 watts from RF power amplifier 10. One suggested receiver Kenwood THD-7 11. Antenna Pair of quarter-wave monopoles fed 180 degrees out of phase The Starshine 3 transmitter was derived from the SEDSAT-1 Mode L Transponder, which has been operating on orbit since 1998. Both systems were designed and built by Cynetics Corporation. The data collection system was built by the South Dakota School of Mines and Technology. The antenna was built by the Physical Science Laboratory of New Mexico State University.