ANDE POWER SYSTEM ENERGY BUDGET 1 Apr 2004 ---------------------------------------------------------------- Updated 17 May 05 Bob Bruninga Updated 27 May 05 added actual flight build currents. Updated 29 May 06 Noted 0.05 mA leakage current in each current sensor. Total is 0.2 mA for the spacecraft. Compared to an average 50 mA when operational, this is about 1 day mission lost for each 250 days connected. The original prototype currents were higher than expected. The original (Oct 2001) baseline was 30 mA average current for the life of the mission. Now we estimate 50 mA total for both sides. Original TNC/RX drew 78 mA. Removing audio amp chip saves 12 mA down to 66 mA instead of the designed 45 mA. TNC was drawing 32 mA instead of 15mA as designed. Timer circuits were drawing 10 mA instead of 1mA. Final flight currents are 5.5 mA in standby per side just about as desired. BATTERY SYSTEM: Lithium-primary Battery Mass: 11.2 Kg Battery Construction: 112 Cells Tadiran TL-5930 Each cell is 93 g and 33 x 62 mm Battery volume: 7562 cu cm Battery configuration: 28 4-cell strings in parallel Battery volts: 12 volts (14.4v no load) Battery safety: Every 4-cell string fuzed individually Battery capacity: 532 AHrs (7448 WHrs at 14 volts) ANDE Telemetry/Command system: nominal dutycycle 10% ontime result Average Percent System current standby with-users USAGE CURRENT ------ ------- --------------- ---------- ------ -------- ------- Rcvr A 35 mA 10% [1.5s ON ] 10% 20% 7 mA 14% TNC A 30 mA 10% [15s off] 10% 20% 6 mA 12% XMTR A 600 mA 20% 2% 12 mA 25% LASERS 350 mA 3% over Maui 10% 0.3% 1 mA 2% Timers 3 mA 100% 100% 100% 3 mA 6% Volt TLM 0.2 100% ea (2) 100% 100% 0.4 mA 1% Temp TLM 0.7 10% ea (6) 100% 20% 0.4 mA 1% 5v ref 0.9 10% 100% 10% 0.1 mA 0% Counter 1.2 100% 100% 100% 1.2 mA 2% 32 mA Note STANDBY current design is 5.1 mA Actual flight value on Side A is 5.2 mA (17 May 05) Rcvr B 35 mA 3% [1.5s ON ] 7% cmding 10% 4 mA 8% TNC B 30 mA 3% [45s off] 7% 10% 3 mA 6% XMTR B 600 mA 3% backup only 7% 1% 6 mA 12% Timers 3 mA 100% 100% 100% 3 mA 6% Volt TLM 0.2 100% ea (2) 100% 100% 0.4 mA 1% Temp TLM 0.7 3% ea (6) 100% 3% 0.1 mA 1% 5v ref 0.9 3% 100% 3% 0.03 mA 1% Counter 1.2 100% 100% 100% 1.2 mA 2% --------------------------------------------------------------- ---- Total 50 mA Growth compared to original proposal 67% NOTE: 30% of the prototype power was in the on-always timers, counter and TLM. As of 20 March 2004 we made the following design changes: 1) Note the Speaker Amp and RS-232 go away in flight configuration 2) Doubled Voltage divider resistors (saved .4 mA always) 3) Quadruple the Counter D/A resistors (Saved 1.8 mA always) 4) Double Temp Sensor impedance to 10k for R2 (saved 0.6 mA) 5) Install CMOS 555 timers (saves 6 mA) Actually, the originals measured a whopping 6 and 8 mA each (spec says 15 mA so clearly a CMOS version was necessry. (less than 1 mA resulted) Battery life: 532 AHrs/50 mA = 10,000 hours = About 420 days. The total life is drastically dependent on the usage duty cycle. The above figures assumed a general scenario. Actual usage could be greater or less. Typical and target values could allow for more than 1 year life and still support nominal communications via the PCsat- style operations... The side B is dormant except for its 1.5 second wakeup every 45 seconds. Unless the A side fails, the B side is not going to be used for any user load. But for good telemetry from both sides of the spacecraft, we will usually turn it on on every command pass. THus we increased its duty cycle significantly from the original estimates. Bob Bruninga USNA Satellite Lab