FIRST APPROXIMATION STARSHINE POWER BUDGET WB4APR ------------------------------------------------------------------------ DOWNLINK is 1200 baud AX.25 packets XMTR is a 2W FM transmitter on 145.825 MHz It will transmit a minimum of a single 1 sec packet once a minute that contains a minimum subset of telemetry. In addition, when it is over populated ares of amateur satellite operators (USA, Europe, Japan, Australia) it has the option of relaying users mesages. The power requirements are summarized as follows. These values have been averaged to a 12 volt system assuming 80% efficient power conversion. Device current dutycycle average comments -------- ------- --------- -------------------------- CPU 5 mA 100% 5 mA Receiver 30 mA 10% 3 mA PV exp 30 mA? 10% 3 mA Processor power GPS 200 mA 3% 6 mA on for only 30 mins a day. XMTR 400 mA 1.2% 5 mA minimum telemetry 400 mA 10%*10% 4 mA User load worldwide 400 mA 2% 8 mA PV experiment data ------- Total power required at 12V is 34 mA or about .4 Watts or about 10 Watt- Hours per day for a nominal Starshine. Thus for a 1000 W-Hr primary battery, we get about 100 days operation. To get a feel for the size, about one cubic foot of Energizer Alkaline batteries would be good for about 4000 Whrs at 12 volts, at 32 Kg. Using the above Comm system baseline, this would be good for about 400 days. Probably about right for a Shuttle deployment below ISS. Other refinements to the PCsat baseline that could extend battery life: >1) Operate only in daylight (Schools in session) 20% savings >2) Change to very low power "pager" receiver 30% savings >3) Drop transmitter to 1W vs 2W 20% savings >4) Operate TNC on 3.3 vs 5 volts 10% savings >5) Minimize operating areas (USA, Europe only?) 10% savings. >6) Other battery technology 30% savings? >7) Put system in sleep mode except over GND STN Factor of 20 savings! The SLEEP mode only wakes the system up for 5 seconds out of every minute. If a Ground Station connects during that time, it will stay awake for the full 10 minute pass and send telemetry once a minute and allow for full command and control. In Sleep mode, the power duty cycle is reduced to a daily average power requirement of only 0.1 Watt! This can be met with only about 1.2 square inches of solar cells. de WB4APR@amsat.org, Bob