TO: IARU Amsat Frequency Coordinator TO: IARU Satellite Advisor Gentlemen, The US Naval Academy and Weber State College have been offered a GTO launch opportunity if we can build a payload in 2 months for delivery by 14 Feb 1998. Our payload takes advantage of this unique circumstance and fullfills a very attractive nitche in the Amateur Space program. Here is the basis for our frequency request: SPACECRAFT: DEMOSAT. A mass-equivalent test launch to GTO from the first test flight of the Sea Launch system using a Russian built Zenit booster and [ TBD ] GTO transfer vehicle. THe DEMOSAT is a 9 foot by 3 foot mass equivalent passive payload. We have been offered a ride to a 36,000 by 655 km GTO orbit by the NASA Sponsored University Space Research Association for a 15 kg payload. The remainder of this proposal will address our 15 kg payload attached to this DEMOSAT. Details on our project are on our web site at: http://web.usna.navy.mil/~bruninga/natsat.html MISSION: A space based AX.25 AFSK 1200 baud digipeater for relaying mobile GPS/Status reports and messages from vehicles on remote expeditions or in areas without existing terrestrial APRS (Automatic Position Reporting System) Infrastructure. SPACE STATION: Dual-redundant 10W Transmitters fed by two Kantronics KPC-3+ TNCs operating only as DIGIPEATERs for individual APRS UI packets. As half-duplex digipeaters, the transmitter duty cycles will be less than 40% and closer to 30% under full load. When the satellite is at perogee, or out of view of all USA and European users, it is silent except for a 1 sec telemetry packet once every 5 minutes or so. EARTH STATIONS: Intended users are high power 250W EIRP, but very low duty cycle mobiles using omni antennas who transmit a single one-second packet once every 15 to 60 minutes (depending on the number of users). Thus they offer little interference potential to any other local terrestrial OR satellite users on the uplink freuqnecy band. Two meters is the required uplink band because of the omni-to-omni nature of the mobile to satellite geometry. The additional 9 dB loss required for 70 cm is completely impractical for this mission. N.AMERICAN EARTH STATIONS UPLINK: The 2 meter 144.39 MHz frequency was recently coordinated Nationwide in both the US and Canada by the ARRL, AMSAT-NA, and Canadian groups for APRS type GPS/Status reporting. This frequency will allow joint shared operations with our uplink and all existing users. REGION 1 and 3 EARTH STATIONS UPLINKS: We should not consider the 144.39 uplink from any other continents where it is not currently available for FM packet since it may create discontent. We must, however, offer an alternative. One good idea is to use our 2m downlink frequency for the alternative 2m Uplink. THis sharing is possible due to our half-duplex digipeating. SPACECRAFT DOWNLINK: Our downlink requirement is unique. Due to the nature of the existing worldwide APRS Internet linked system which already distributes all APRS packets world wide via the internet, (Telnet to 199.227.86.221 port 23) we only need a few high quality downlink receive stations to feed the received packets to the worldwide APRS Infrastructure and all users worldwide. Thus we are not targeting individual users, and so our downlink has the advantage of spatial diversity. Only 1 receive site out of N sites must receive each packet for success. This ability to contend with large amounts of QRM for any individual receive site, makes it possible for us to share our donwlink frequency with almost ANY other users or systems. (Even 144.39 with over 500 permanent digipeaters and thousands of users) We propose an initial single 15 KHz wide downlink FM AFSK in the 145.8 Amateur Satellite band. The signal power on the earth will be about -128 dBm and due to the multiple internet linked ground stations, we can share the frequency with ANY other LEO amsat applications. Our weak signal will be nearly undetectible by most users unless they are running OSCAR-10 class stations with beams pointed towards our spacecraft. We think our downlink could share a number of frequencies currently in use, such as the 145.825 DO-17 downlink. On this DOVE frequency, even the full power European uplinks would not bother existing DOVE listeners, since each uplink station will only transmit ONE ONE-SECOND packet once every 15 to 60 miuntes. And such an uplink station would only be a mobile on the ground level far from any existing APRS infrastructure! (and all other hams). Thus, the uplink would not interfere with someone listening for DOVE at all. REMINDER: Uplink stations for this satellite are isolated ground level stations FAR from any existing population areas. As an example, 95% of the USA poplation already has full APRS infrastructure in place so there is no incentive for a user to report once every 15 or 60 minutes using a high power 250W EIRP transmit only station, when he can already communicate worldwide both send and receive using only a 5 watt walkie-talkie at a once-a-minute rate via the APRS infrastructure. Conversly, although 95% of the population is convered, only 30% of the land area of the USA and none of the rest of the world is covered, so there is a definate mission requirment for high power mobiles on distant travel to report health-&-welfare position and status. DETAIL DESIGN: Currently we are conisdering two completely independent digipeaters as detailed below. This view is at apogee. The Spacecraft is about 9 feet long and 3 feet in diameter and spinning about the Horizontal whip axis. Thus, the Horisontal whip is always in view and horizontal, and the Vertical whip is usable (within 3 dB) 50% of the time. | Vertical Whip | ********************** | * / -----| *< motor end Horiz whip | * \ ********************** There is one solar panel on the top (left end here) and four on the four sides. These four are angled at 15 degrees to the right so that we can see the sun during that time of year when the Sun is off the motor end. There will be two complete and independent TNC/RADIO/BATTERY systems: (I am using 145.825 as an example satellite downlink,it is NOT APPROVED) Horizontal system RECEIVES on 144.39 and TRANSMITS on 145.825* with 10W Vertical system RECEIVES on 145.825 and TRANSMITS on 145.825 with 10W Horizontal 144.39 is for use in the USA and 145.825 is for regions 1 & 3. Vertical antenna will be rolling and will be masked or nulled 50% of the time. It is assumed that each system will not generally be used at the same time. The satellite will spend 12 hours over one hemisphere and then 12 hours over the other. Peak power system and downlink loading will occur when the APOGEE is over the Atlantic and can see both the USA and European users. THere are no or very few users in the equatorial areas where perogee occurs. Operations near the Earth and perogee are not part of the design objective. TUMBLING: Another reason for the orthogonal antennas is that the spacecraft will eventually tumble and then orientation becomes more or less random. RESETS: The Failsafe RESET timer will watch the PTT. If there is a PTT at least once every 5 minutes (the Telemetry Rate), then nothing happens. If PTT does not pulse for 1/2 second once every 5 minutes, then a power-up reset is performed. There will be a DTMF decoder with backup reset possible. Each TNC has two OUTPUT switches. THese weill be used to cross connect either of the transmitters or battery systems. Analog telemetry using the built-in KPC-3 telemetry channels. Although only 5 channels are available, we are using a switch connected to the LED driver to select between two banks of telemetry with the LEDS ON/OFF command. The table below represents one system. The telemetry is duplicated in the other system. LEDS OFF LEDS ON -------------------------- ------------------------- Ch1 +Z Top panel current Ch1 Battery Temp Ch2 +X side panel current Ch2 X array Temp CH3 +Y side panel current Ch3 Y array Temp CH4 System current CH4 Electronics Temp CH5 Battery Voltage CH5 RF power out The TNC will be configured for DIGIPEATING of UI packets addressed via the generic space callsign of "APRSAT" only. The TNC will originate only 3 packets of its own, an ID text, the telemetry packet and probably a 1-line Keplerian element set. FUTURE GROWTH: Notice the asterix (*) by the 145.825 downlink for the 144.39 USA system. We would propose to include a 144.39 downlink crystal as well for possible future use whenever the satellite is not in view of Europe or if the weak -128 dBm FM signal is shown to be of no consequence to existing European 144.39 coordinated users. By enabling the 144.39 downlink (only with future perimission of all the powers-that-be) we would improve our system capacity by 25% by not having collision contention on the single 145.825 (proposed) downlink. We think this is a unique opportunity, a unique design and a unique mission that is current with the rapid growth of APRS in the amateur packet community. Not only does it offer functionality in the high density HAM population centers of the USA and Europe, but it also provides low-duty-cycle position/status reporting for travelers and expeditions worldwide. None of this is possible from 36,000 on a non attitude controlled spacecraft without the use of 2 meters for both uplink and downlink. Respectfully Submitted Bob Bruninga, WB4APR, 410-293-6417 days, 410-553-6021 eves. US Naval Academy Satellite Lab, 410-293-2591 FAX, wb4apr@amsat.org 590 Holloway Rd Annapolis, Maryland 21402.