?? ATVISS ? Amateur Television on the International Space Station
To provide hardware for inclusion in the permanent ARISS station to enable ground based users access to and some control of, video cameras on board the space station.
To so design the downlink methodology and modulation system to enable the pictures to be obtained with relatively simple ground equipment.
To provide a system which is designed to be ideal for incorporating into demonstrations of amateur radio to capture the interest of incomers to our world.
To provide a system which cannot sensibly be duplicated or replaced by the Internet!
Both the Mir space station and a number of SAREX Shuttle missions have demonstrated SSTV (slow scan) Television. The SSTV transmissions from Mir during late ?98 and the first part of ?99 have created a dramatic increase in the level of interest in the mode and in the amateur space service.
The saying of "a picture is worth a thousand words?" has never been more true than the area of space exploration. The moon landings and the Mars Rover bear ample witness to this.
A large number of Amateur Radio Satellites have already demonstrated taking "still" pictures of the earth from space and these use devices which can also be used for "moving" pictures.
Fast Scan Amateur Television (FSTV) is activity that started in the late 1940?s in Europe and the USA and generally uses standard broadcast systems to maintain compatibility. Current there is ATV activity some 20 or 30 countries around the world. This activity centres on the 70cms/23cms/13cms and 3cms bands both with simplex and repeater operation. There are, perhaps, some 300 ATV repeaters around the world.
Although the best FSATV DX record currently stands at some 2000+miles on 70cms and 500+ miles on 3cms, generally ATV contacts are local in nature.
There are number of national ATV societies around the world (BATC in the UK, AGAF in Germany, HBATV in Switzerland etc) and their total membership is probably in excess of 5000 amateurs, perhaps similar to the worldwide membership of the various AMSAT groups?
One, or more, colour cameras would be placed, externally, at suitable locations on the space frame of the station.
The ISS being stabilised, these cameras would be essentially "earth pointing" and therefore generally not vulnerable to exposure to direct sunlight.
The cameras would be capable of pan/tilt and zoom operation.
The camera(s) would be connected, by an umbilical cable, back to a central power supply, control and transmission unit.
The ground station would command the transmission on for a defined time period (say 5 minutes) by sending a simple command (say a DTMF tone). Additional commands would operate the pan/tilt/zoom system as required by the ground operator.
Alternatively a packet system could be devised for control which would also relay the control sequences received and currently active back to the ground. This would enable the ground station to understand what was happening with the system and other ground stations could also see who was currently commanding the camera.
The latter system would also enable the system?s "health" to be monitored by telemetry carried on the same carrier.
Maybe the APRS system would be suitable/could be extended to provide this functionality.
When not under ground command the system could beacon every 2 mins for, say, 10secs with camera video or caption.
A limited number of ground based "Control" stations could also upload captions and operating instructions which could be transmitted as part of a testcard sequence. (This follows established ATV repeater practise)
The camera would, when the station is manned, be under the control of the astronauts on board.
A camera could have a low light level capability to show "night scenes" of both the ISS and the ground, perhaps for light "pollution" measurements.
The "radio" equipment would consist of:
Command receiver and decoder ? Simple AFSK 1200Bd packet system would sufficient. The uplink could be just below 438MHz if this would avoid the Pave Paws type radars?
Command relay and telemetry transmitter ? Would be to the same standard as the receiver and work in simplex mode on the same frequency.
The video could be, perhaps initially, could be colour SSTV as demonstrated by MIR .If a world-wide allocation on 2 metres was available this would be ideal, but failing that, 10 metres (subject to space for the TX antenna) would allow the use of simple, scanner type, receivers.
There is, currently, no adopted standard for digital FSATV. A digital system would be the most appropriate in terms of definition/power budget/spectrum usage. Until such a system is practicable the best system would be FMTV as currently used by TV amateurs for most terrestrial operation above 1GHz. ? The transmitted bandwidth would be, perhaps, some 10MHz if analogue or 4/5MHz if digital. The band of choice for this would be 13cms as it is already in common use by ATV operators in many countries. Antenna beamwidth/gain would be an issue.
Selection of 525/625 line standards for analogue signals could be by ground control or by onboard GPS positioning data.
This concept is based upon the premise that existing and potential amateurs will be "thrilled" by the possibility of seeing what is happening on and around the ISS and on the earth below.
They would be further interested in the possibility of "commanding" a part of the ISS themselves directly.
Although the pictures could be relayed via the internet, the relatively low height of the ISS would require a large network of ground stations to provide a reasonable level of service.
There is nothing described above that is beyond current technology and it should therefore be possible for such a system to be created quickly and, relatively, cheaply.
Graham P Shirville G3VZV, August 99. Version 1.0