Communication System DINO Peer Review July 9, 2003

Subsystem Block Diagram

Power Requirements Daytime Operation Receiver: 0.54 W (6 V, 90 mA) always. TNC: 5.52 W (13.8 V, 400 mA) always. Transmitter: 8.4 W (6 V, 1.4 A) for approx. 2 minutes, otherwise same as Receiver (0.54 W).

Power Requirements Nighttime Operation Safe Mode Receiver: 0.54 W (6 V, 90 mA) always. TNC: 5.52 W (13.8 V, 400 mA) always. Transmitter: 8.4 W (6 V, 1.4 A) for approx. 4 seconds, otherwise same as Receiver (0.54 W). Safe Mode Same as nighttime.

Calculating Transmission Time Time needed to send one packet: 10 bits/byte * 256 bytes/packet  9600 bits/sec = 0.267 sec/packet Total transmission time (assuming 50 kB per pass during daytime): 0.267 sec/packet * 50 kB/pass  256 bytes/packet = 52 sec/pass

Transceiver Trade Study: Four Choices ICOM IC-ID1 1.2 GHz digital Pros Allows for small antenna Built-in TNC with 64-128 kbps baud rate USB interface Cons Expensive Only one frequency band: need half-duplex comm. Newly released, untested, unlicensed by FCC Needs new ground equipment

Transceiver Trade Study Kenwood TH-D7 dual band 70 cm/ 2 m Pros Operates in 2 frequency bands One third of the cost of the ICOM radio Compatible ground equipment already set up Previous experience from other missions Cons Max. baud rate of 9.6 kbps. Requires larger antenna than ICOM Uses RS-232 interface

Transceiver Trade Study TEKK SD-5200 synthesized radio and TEKK KS-960 crystal radio Pros Can be set to one frequency by the manufacturer: no actual programming required (unlike Kenwood) Currently being proven in space flight on Stanford’s Quakesat mission Significantly cheaper than the Kenwood radios Cons Only UHF version available: so we would need a different radio for VHF (no longer advantageous)

Design Decision Two Kenwood TH-D7 radios: one for uplink, the other for downlink. Reasons Only choice that allows two distinct channels for uplink and downlink, respectively. Much better to use same model for both channels 9.6 kbps should be a sufficient baud rate for the purposes of this mission No idea when the ICOM 1.2 GHz radio will ever be available for our use.

Antenna Trade Study Monopole Pros Cons Simple design Does not take up space on the satellite’s surface Cons Deployable Could be very long (~50 cm)

Antenna Trade Study Patch Pros Cons Preferable gain pattern Non-deployable Cons Could occupy a lot of space on nadir surface More complicated design process More expensive