Amateur Satellite

Amateur Radio
Communications Satellite

Amateur radio communications has now entered the satellite age. The United States, European countries, Russia, and other countries have already launched satellites for amateur radio communications.
Japan followed suit by launching its first satellite in August, 1986. In 1990, JAS-1b, the second amateur satellite was launched and thrown into orbit. Then succeeding it, a third satellite JAS-2 was launched in August, 1996, carried out with great efficiency. With this expansion of hams' dreams, the JARL is expected to promote international cooperation in diffusing knowledge about outer space.

The new satellite

"JAS-2"
JAS-2 was successfully launched on August 17, 1996, by H-II launch vehicle along with earth observation satellite "ADEOS" from Tanegashima Space Center of NASDA. JAS-2 is prepared to succeed "JAS-1b" which was launched in February 1990 and still working.

Lift-off time was 1053 JST ( 0153 UTC ). After some 38 minutes, JAS-2 was separated from the vehicle, and power of JAS-2 was turned on. The event was first reported by NASDA, then a few minutes later, reception report of JAS-2 signal was transferred to the Space Center from Showa Base at Antarctica through INMARSAT link, and Control station in JARL headquarters in Tokyo cheered for the report.

After waiting one hour, clear signal "HI HI ......" came out from the speaker. Immediately Morse code recording started. Letter by letter, paper was filled with two digit telemetry data, and analyzed Telemetry data showed that condition of JAS-2 seemed normal. After this pass, JAS-2 could not be seen in Tokyo for about six hours due to orbital condition.

In the evening, the control station got AOS at 2056 JST. A number of commands were transmitted and verified. Next pass was around 2241. During these passes, preliminary orbit prediction was done using Doppler shift of beacon frequency. Doppler shift curve showed fairly good fitting with calculated one.

After several passes, staff had a confidence of accuracy of orbital parameters. These Keps were almost the same as the Two-lines first announced by NASA on August 21.

August 18, at the pass of beginning 2146, digital transponder were turned on, and there came a familiar tone of 1200bps packet. For trial, some messages were wrote into the transponder, and then it was read out. Okay, BBS must work well. In next pass, some messages were written in BBS from foreign countries.

Since the day JAS-2 was launched, JARL has been conducting a variety of in-orbital tests on JAS-2's several functions, and confirmed capabilities of Power Supply System, Communication System, Attitude Control System and Thermal Control System.
Following factors which have become obvious.

(1) Power Supply
Maximum electric current generated by solar cells is 1.5A and Bus voltage is from 13.5 to 17 V. It keeps more than 23W.

(2) Communication System
It has been confirmed that all equipment of analog transponder, digital transponder ( 1200bps/9600bps ) and digi-talker were in normal. However, Mail-Box comes to a stop after several days. After numerous simulation tests, it came to the conclusion that the fault could be traced to JAS-2's "error correction system" which is made to prevent unexpected data transformation. So, on April 8, 1997, final revised software was up-loaded to solve the problem.

(3) Attitude Control System
There are no problems in Solar Sensor, Geomagnetic Sensor and Magnetic Torquer. And both Nutation Damping and Spin Control functions are working well. Fading in down-link signals has almost vanished with Nutation Damping System. Satellite's attitude will be carefully monitored and controlled to increase solar cell power and to keep good thermal condition.

(4) Thermal Control
Temperature of satellites' main structure indicates between 4 and 18 degrees ( Celsius ), battery temperature keeps between 6 and 20 degrees, and solar cell temperature indicates in-between -11 and +22 degrees. These are stable and healthy as planned. The solar cell temperature has gone up 3 to 5 degrees in comparison with the temperature when launched because of the earth comes closest to the sun in Jan.

Dimensions

* Orbit
Apogee : 1320 km
Perigee : 799 km
Inclination : 985 deg.
Period : 106.5 min

*Analog Transponder ( linear transponder for phone and CW )
Uplink 145.90 to 146.00 MHz, 100 kHz pass band
Downlink 435.80 to 435.90 MHz, 100 kHz pass band
Beacon signal at 435.795 MHz, modulated by CW TLM Total transmitting power 1W ( of which beacon is 100 mW )

*Digital Transponder (store-and-forward packet processor)
Uplink 145.85, .87, .89, .91 MHz, four channels
Downlink 435.91 MHz, one channel
Bit rate 1200 or 9600 bps, alternative operation 1200 1200 bps up Manchester coded FM, down bi-phase PSK 9600 bps FSK G3RUH both uplink and downlink
Total transmitting power is 1 W.

*Digi-talker ( audible information by voice with a hand-held transceiver )
Source information in PCM from the control station.
FM Voice 435.91MHz

*Data Processor
CPU V50, static RAMs of 2MB
BBS, digi-talker, telemetry and command data processing and automonus operation.

*Structure
Aluminum alley
44 cm wide and 47cm high, sphere-like 26 face polyhedron 50 kg.

*Power Supply
Gallium-Arsenide solar cells of 2 x 2cm and 2 x 1 cm Nickel-Cadmium storage battery of 6 AH.

*Attitude Control System
Sun-sensor, geomagnetic sensor, magnetic torquer and attitude control electronics

*Antenna
Folded and loaded turnstite for 145MHz band
Folded turnstite for 435MHz band

HOME

Sub Menu

Page Top