ANDE COMMAND AND CONTROL SYSTEM WB4APR ------------------------------------------------------------------- 27 June 2002 This Naval Academy command and control system for ANDE has been flight proven on PCsat and will provide the following capabilities on orbit with the minimum power requirements suitable for this mission: 1) Routine telemetry every 1 minute when in view of command station 2) Telemetry of 5 analog parameters (0-5 volts) 3) Three on/off command channels and bidirectional RS-232 channel 4) AX.25 1200 baud compatibilitiy with all existing packet systems and the worldwide internet linked APRS gnd stations on 145.825. 5) PCsat style communications worldwide at low duty cycle 6) Reception by student stations with only a whip antenna. 6) Average power requirement of only 0.2W The average power requirement of 0.2 watt for a mission life of one year can easily be met with either of the following two power systems: * Ten 1.5" square solar panels equally distributed on the sphere * OR, the equivalent of 120 Alkaline D Cells. The extremely low power budget is met with the following operations plan which does not sacrifice any significant operational functions of the PCsat type mission but achieves a 20 to one power savings. 1) Except for a microwatt timer, all electronics are off 2) Once every 20 seconds for 2 secs, the TNC and receiver are powered up. 3) If no one connects to the TNC, then it powers back off. 4) If someone connects, the CONNECTED state holds the system ON. 5) While SYSOP is connected, TNC and RX are on, the system is fully usable like PCsat. It will send once a minute telemetry, it will respond to the 3 ON/OFF BIT commands, and it is optionally available to users to use as a packet relay. POWER BUDGET: To determine the power budget, the Satellite is assumed to be in view of each command station on 4 passes a day. There are about 6 full time commmand station areas, East USA, West USA, East Europe, West Europe, east Australia and Japan. The satellite may be used in other locations, but the duty cycle will be insignificant to these six. Each such pass is assumed to last 10 minutes. Thus the total access times average to about 120 minutes a day for an 8% dutycycle. All the rest of the time, the TNC/Receiver are only waking up for 2 seconds out of every 20 for another 8% duty cycle. The transmitter is assumed to transmit 10 Telemetry packets, 10 overhead packets, and 10 user packets per pass for a total of 30 in 10 minutes for a 5% duty cycle per pass. Receiver - 30ma @ 9 volts @ 16% = .06 W TNC - 15ma @ 9 volts @ 16% = .03 W XMTR - 900ma @ 9 volts @ 5% of 8% = .05 W Total AVERAGE Power = .14 W This power can be met with the equivalent of 120 Alkaline D Cells (120* 16 AHrs * 1.5 volts)/(365*24) = .2 W for one year or 10 evenly spaced solar panels of 0.2 W each. An illumination factor of 1.8 is assumed which accounts for the cosine-theta illumination of multiple panels and a 200% charge factor is assumed to make up for the 70% charge efficiency and 45% maximum eclipse. This 0.2 W solar panel requirement can be met with about 1.5 square inch of silicon. To maximize active surface material, only 4 PV cells per panel are used to give a self regulating charge to a single 1.2 volt NICAD cell. Each of the 5 NiCd cells is connected to two solar panels on opposide sides of the spacecraft to guarantee sun. Some of this data is obsolete and needs to be revised... de WB4APR, Bob Bruninga