Site: Mitsubishi Electric Co.
Kamakura Works
325, Kamimachiya Kamakura
Kanagawa 247, Japan
http://www.mitsubishi.com

Date Visited: June 4, 1997

WTEC: W. Brandon (report author), C. Bostian, A. Mac Rae

Hosts:

BACKGROUND

It was noted that 1997 was perhaps a very special year for both the United States and Japan, marking the beginning of Globalstar and Iridium, and the Mars spacecraft; and for Japan, Superbird C (scheduled for launch in July 1997), COMETS (scheduled for launch in August 1997), the ETS VII unmanned docker, and the 10 meter MUSES-B antenna deployment. As prime contractor for about 20 spacecraft, Mitsubishi Electric Company (MELCO) has accumulated 80 years of on-orbit experience. A video on MELCO revealed the breadth of the company's activities towards improvement of daily life in the home, transportation, defense, manufacturing, space, and communications (listed below).

Advancement of the quality of society is the 21st century vision. Distinctive blue jackets underscored the long-term team commitment to the DASH 2000 goals (dynamic, active, speedy, humanity). Communications and information processing will transform society and MELCO activities in GMS mobile telephone, optical fiber products (both trunk line and subscriber line), electronics (ultrasonics to microwave and optical), and medical diagnostics are major activities. A comprehensive manufacturer, MELCO has produced the high speed Shinkansen trains, a spiral elevator, a "retinal chip" module, the MISTY encryption algorithm and over 16,000 microwave antennas. Defense products include improved Hawk and Sea Sparrow missiles and search and rescue radios.

MELCO produced the first Japanese spacecraft (ionospheric sounder, 1976) and today has many contracts, including the Japanese Experiment Module (JEM, part of the International Space Station program). It is a major component and subsystem supplier to the world's prime contractors, and is well established as a leading world company in satellite communications.

R&D Activities

Satellite Antennas

Progress and heritage in communications antennas were documented by models in the company museum.

"Conventional" Antennas

MELCO antennas include the large (C-band) CS-3 horn reflector of impressively lightweight; a Ku-band dual-polarized gridded reflector; INTELSAT-7 C-band antennas; 40/50 GHz antennas for ITALSAT F1; the ADEOS ISL antenna (1.35 m diameter, better than 0.2 mm rms surface accuracy), and the COMETS ISL antenna (3.6 m diameter, better than 0.3 mm rms surface accuracy).

Large Reflector Antennas

MELCO produced the 10 m deployable reflector for the MUSES-B (very large baseline interferometer) satellite that will operate at L-band, C-band, and 22 GHz. The surface accuracy is 0.5 mm. An aperture efficiency of 68% was quoted. The antenna weight is less than 230 kg.

MELCO proposed a 10 m deployable reflector design for ETS-VIII but it was not selected. The effective aperture diameter would have been 8 m center-fed while the selected design is offset-fed.

MELCO built an R&D model of an unfurlable offset Cassegrain antenna with a 3.5 m diameter and a gain of better than 34 dBi.

Due to the high surface accuracy achieved with deployable reflectors, MELCO has no experience with inflatable antennas.

Active Phased Arrays

MELCO built a "90-element" phased array for ETS-VI. The radiated power was about 1 W per element or 90 W total. It was also described as having 19 elements, each of which is a 7-element microstrip subarray. It transmitted at 2.1 GHz with 26.2 dB gain and received at 2.7 GHz with 27.2 dB gain. The EIRP was 33.3 dBW and the G/T was -4.4.

Arrays for Synthetic Aperture Radar (SAR) Satellites

MELCO has produced the antenna for an SAR radar for a Japanese environmental satellite. The radar frequency is 1,275 MHz. The antenna produces a 1.05 x 5.6 beam having 33.5 dB gain. The antenna is 2.2 m x 12 m and weighs 132 kg.

Gigabit Satellite Antenna

MELCO is developing a Ka-band active phased array antenna for CRL as part of the Gigabit Satellite Program with projected launch date of 2002. The transmitting antenna will have 5 scanning spot beams and transmit at 20 GHz (18.75 GHz, bandwidth 559 MHz) with an effective aperture diameter of 2.2 m. The receiving array will operate at 20 GHz (28.55 GHz–559 MHz) with an effective aperture diameter of 2.1 m. The antenna will scan 1.5 degrees and transmit a total power of 500 W. The gain will be greater than 55 dBi. The total number of elements is 2,500 (count includes all of the subarray elements). The current plan is to use waveguide horn radiators. The element spacing will be 3 wavelengths. This is acceptable since the scan angle is rather narrow. The total cost of the antenna is about $50 million.

The phased array described above will operate with an onboard processor that will connect 20 SCPC uplink channels to 5 TDMA downlink channels.

The design goal for the SSPAs used in this array is 20% efficiency for multicarrier operation (5 TDM processed channels; see onboard processing section below).

Solid State RF Power Amplifiers (SSPAs)

One of the world leaders, MELCO is producing solid state power amplifiers (SSPAs) for the ICO system satellites. The growing use of phased array antennas leads to satellites with large numbers of low power SSPAs (5 to 10 W for ICO array elements). MELCO's current power capability is 15 W per SSPA.

Onboard Processing

An ATM baseband switch is employed in a processor that converts 20 SCPC uplink channels to 5 TDM downlink channels. A 5 x 5 IF matrix switch is also being developed. In response to a question about onboard processing, WTEC panelists were referred to the catalog but advised that the catalog is old. New equipment is being developed and delivery times are getting shorter.

Solar Panels

MELCO used GaAs solar cells on CS3 for high efficiency (18.6 % at that time) on a small satellite. MELCO currently manufactures 20 kW solar arrays that are 14.7 m long x 2.4 m wide, using four panels, for Afristar and Telstar. For even higher satellite power, panels that deploy in two dimensions are being designed.

Heat Pipes

MELCO produces heat pipes for many programs.

Ion Engines

COMETS will fly a 25 mN xenon engine. MELCO is looking at 100-150 mN performance level. No problem with electrostatic charge accumulation associated with ion engine operation has been observed.

Low Noise Amplifiers

For NSTAR MELCO produced 30 GHz LNAs with a NF of 2 dB or better. The customers desire Ka-band LNAs with 1 dB noise figures. MELCO has developed 100 GHz LNAs with a 5 dB NF (presumably experimental).

MELCO is evaluating the use of Si-Ge for LNAs.

Attitude Control

MELCO is getting 0.05 spacecraft pointing accuracy at GEO, and 0.3 at non GEO, using zero momentum control systems (0.05 roll and pitch, and 0.15 in yaw).

Data Handling

MELCO developed a packet data handling system for ETS-VII, with data rates of 2 Mbps. The company is now looking at 6 Mbps and has a goal of 120 Mbps.

references

Mitsubishi. 1996 Corporate Profile. 1996. 38 pp.

____. Meeting agenda, 4 June 1997.

____. 1996 Mitsubishi Kamakura Works. Product photographs.

____. Space Activities - Mitsubishi Electric. n.d. Color copies of viewgraphs.

____. Space Activities, 1997, 18 pp. Booklet.

____. Satellite-Borne Equipment. n.d. Overview catalog of flight hardware.


Published: December 1998; WTEC Hyper-Librarian