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Satellite Detail - Fuji-OSCAR 20

Launch Pad

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Fuji-OSCAR 20
(JAS 1B)

Spacecraft Summary

OSCAR Designation:	Fuji-OSCAR 20	Oscar Number:	FO-20
International Designator:	1990-013C	Norad Number:	20480
Common Name:	JAS 1B	Alternate Name:	Fuji 2
Satellite Type:	Microsatellite	Launch Date:	7 February, 1990
Launch Location:	Tanegashima Space Center	Launch Vehicle:	H-1
Apogee:	1744.00	Perigee:	912.00
Inclination:	99.05	Period:	112.21
Dimensions:	47 x 44 x 44 spheroid	Weight:	50.000 Kg
Organization:	Japan Amateur Radio League

Frequency Information


Mode V/U (J) Linear Transponder (Inverting): Non-Operational
Uplink:	145.9000 - 146.0000 MHz SSB/CW
Downlink	435.9000 - 435.8000 MHz SSB/CW

Mode V/U (J) PacSat BBS: Non-Operational
Uplink:	145.8500 MHz AFSK 1200 BPS
Uplink:	145.8700 MHz AFSK 1200 BPS
Uplink:	145.8900 MHz AFSK 1200 BPS
Uplink:	145.9100 MHz AFSK 1200 BPS
Downlink	435.9100 MHz AFSK 1200 BPS

Mode U TLM Beacon: Non-Operational
Downlink	435.7950 MHz CW
Downlink	435.9100 MHz PSK

Current Keplerian Elements

FO-20
1 20480U 90013C   09324.09998456 -.00000030  00000-0  32973-5 0  3026
2 20480  99.0605 215.7753 0540635 177.4082 183.0030 12.83361645926907

Detailed Description

Fuji-OSCAR-20 was the second in a series of Japanese Amateur communications satellites having both analog and digital Mode J transponders. The first spacecraft, Fuji-OSCAR-12 was launched on August 12, 1986, and was the first OSCAR satellite to utilize the AX.25 packet radio communications protocol. It was followed by the currently active Fuji-OSCAR-20 several months after FO-12 had to be removed from service due to a deteriorating power budget.

Fuji-OSCAR-20 was launched on February 7, 1990 at 01:33 UTC from the Tanegashima Space Center, National Space Development Agency of Japan (NASDA) on an H-1 two-stage rocket. Its orbit differed slightly from most current OSCAR satellites, being slightly elliptical with a high inclination. This assureed that the satellite will remain in sunlight for the majority of its orbit all year long.

The physical structure of FO-20 was that of a 26 sided polyhedron, with a weight of approximately 50 kg, so it was much larger than the Microsat satellites. Although Fuji-OSCAR-20 used Mode J AX.25 packet radio communications links as the Microsat satellites do, one big difference between FO-20 and the Microsats was that FO-20's packet radio could be accessed without the need for special Microsat terminal software. Any computer or terminal that could be used to access terrestrial packet radio bulletin board systems (BBSs) could be used to access the FO-20 mailbox.

The other big difference between FO-20 and the Microsat satellites was that in addition to the packet mailbox features of the satellite, FO-20 also supported a Mode J analog transponder for SSB and CW communications.

Fuji-OSCAR-20 System Specifications

FO-20 carried two beacon transmitters. The Mode JA beacon was active during periods of analog transponder operation. It operated on a frequency of 435.795 MHz with 100 mW of power, and could carry CW or BPSK information, or could be configured for A0 for Doppler shift experiments.

The Mode JD beacon served as the single AX.25 Mode JD downlink to ground stations, and also carried telemetry in either a ASCII (most often used), or binary formats. The Mode JD beacon operated on a frequency of 435.910 MHz with 1 watt of output power, and used BPSK modulation.

The CW telemetry carried 12 analog status items and 33 status items, while the BPSK packet telemetry beacon carried 29 analog items, plus 33 status items.

The Mode JA analog transponder system consisted of an inverting heterodyne transponder with a bandwidth of 100 KHz, with an uplink in the 145 MHz band, and a downlink in the 435 Mhz band. An uplink power of about 100 watts EIRP was required for access to the transponder, but of course, the more sensitive your downlink receiver is, the less uplink power was required to achieve an adequate downlink signal-to-noise ratio.

The Mode JD digital transponder system functioned as a mailbox using the AX.25 level 2 protocol. It receiveed Manchester encoded FSK on any one of four uplink frequencies, and transmitted on a single downlink frequency of 435.910 MHz at 1200 bps using BPSK modulation. An uplink of about 100 watts EIRP was the minimum required for Mode JD transponder access. The satellite transmitted with 1 watt of transmitter power.

Fuji-OSCAR-20 used circular antenna polarization on all uplink receivers and all downlink transmitters and beacons. The 145 MHz uplink antenna is a ring turnstile antenna mounted below the bottom side panels of the spacecraft, and exhibited a maximum gain of about +0.5 dBi. The 435 MHz transmitting antenna was a turnstile array mounted on the top of the spacecraft, and exhibited a maximum gain of about +4 dBi.

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