Intelsat VI

Last updated

The Intelsat VI series of satellites were the 8th generation of geostationary communications satellites for the Intelsat Corporation. Designed and built by Hughes Aircraft Company (HAC) in 1983-1991, there were five VI-series satellites built: 601, 602, 603, 604, and 605.

Contents

Design

The Intelsat VI satellite was designed as a spinning satellite as had previous satellite designs. The main body of the spacecraft was spun at 30 revolutions per minute (rpm) to impart gyroscopic stability to the satellite in the Earth's gravitation field. A section of the spacecraft supporting the communications payload and antenna was de-spun to allow the antenna to point at the desired location on the earth.

The Intelsat VI series combined two design features of previous HAC satellites, larger solar array and wide body design. [1] The HS376 extended power spinner satellite had an extra concentric cylindrical solar array which deployed after launch to increase the power generating capability of the satellite, and allow for a larger communications payload. The U.S Government's Wide-body Spacecraft was a larger diameter satellite designed to be launched by the Space Transportation System (STS, US Space Shuttle). Thus the Intelsat VI satellite were of a wide body spinning design with a larger solar array, due to the deploy-able array. The later HS393 series of satellites also used the wide body and extended solar array design.

This resulted in a spacecraft that was 3.6 meters (11 ft 10 in) in diameter and approximately 5.2 m (17 ft 1 in) tall as configured for launch on an Ariane 4 rocket. When the spacecraft had arrived at its assigned orbital location, the concentric solar array would be extended (deployed), along with deployment of the communications antenna. The spacecraft would then be 11.7 m (38 ft 5 in) in length.

The Intelsat VI series of satellite were designed to be launched by either Ariane 4 rockets or the U.S. Space Shuttle.

Propulsion

A liquid bi-propellant propulsion subsystem was used on the Intelsat VI series satellites, and used nitrogen tetra-oxide and mono-methyl hydrazine. Four radial thrusters, rated at 22 newtons (N) (5 lbf) are used for east-west station-keeping, and spin-up/spin-down control. Two 22 N axial mounted thrusters provide north-south station-keeping and attitude control. Two 490 N (110 lbf) apogee thrusters were used to provide the apogee boost to the satellite and support re-orientation maneuvers.

Power subsystem

The solar array on the Intelsat VI was sized to provide about 2600 watts of power at the beginning of the satellites life. The Intelsat VI satellites used nickel hydrogen pressure vessel batteries to support operation when the spacecraft was in eclipse behind the earth.

As noted in the introduction, the Intelsat VI series of satellites were designed with a cylindrical spacecraft body which was covered by photovoltaic (PV) solar cells. Since the satellite was rotating at 30 rpm, a flat panel solar array on a side of the spacecraft would be exposed to the sun intermittently and not generate continuous power. With a cylindrical array part of the solar array would always be in sunlight and would generate power for the spacecraft to operate.

Communications payload

The communications payload basically consists of the receivers, filters, amplifiers and interconnection cables or waveguide used to receive radio signals from earth transmitters, and convert them to suitable downlink frequencies, and retransmit the signals back to the earth.

The Intelsat VI satellite used C band at 6 GHz for the uplink/4 GHz for the downlink, and Ku-band at 14 GHz uplink/11 GHz downlink, and had 50 communications transponders which were designed to carry 33,000 telephone circuits, the equivalent of 33,000 two way telephone calls, as well as four television channels. The Intelsat VI satellites used a RF switching network to allow static connections between the uplink channels and downlink channels. The satellite also used a time division multiple access (TDMA) dynamic microwave switching network on channels 1-2 and 3-4 to allow the dynamic cross connection of the channels for TDMA type signals.

Antennas

The antenna system and coverages were designed to be identical for all of the Intelsat VI satellites. This provided simplicity of design and manufacturing for the five satellites in the series, since all the antenna components could be made identical for each of the five satellites. It also allows for any of the VI series satellites to replace another satellite in case of an on-orbit failure.

A 2.0 m diameter reflector antenna was used for receiving C-band signals transmitted up from the earth. The satellite had two C-band "hemi" beam coverages which were designed to cover the landmass areas as seen from any of the orbital locations. Four beams were designed to provide smaller zone coverage for specific areas of the earth depending on the orbital location. Both the "hemi" and zone beams used an antenna reflector 3.2 m (10 ft 6 in) in diameter with a 4.2 m (13 ft 9 in) focal length. A 149 element feed horn array and four switching networks (three were switchable in orbit) allowed the zone coverage to be changed to match the orbital location.

The satellite had a C-band global coverage horn, which provided coverage of the entire earth, for receive and transmission of two channels or repeaters.

The satellite also had two Ku-band steerable spot beams which could be moved to cover any specific area on the earth, and could be re-pointed as needed. The Ku-band spot beams provide both receive and transmit capability.

TC&R

The telemetry, tracking and control (TT&C), or telemetry, command and ranging (TC&R) subsystem is used to receive spacecraft control commands sent from ground control stations, send telemetry from the satellite subsystems to ground receivers, and support tracking and ranging of the satellite by ground stations.

The Intelsat VI satellites used C-band for the TC&R subsystem, and a pair of omni-directional antennas were mounted on a deploy-able boom.

Launch

Via Ariane 4

When launched by the Ariane 4 the satellite would be mounted to a SPELDA adapter (a satellite payload carrier system), which is mounted on the top of the Ariane 4 rocket. A protective shroud or fairing covers the satellite and upper stage and protects it from aerodynamic forces (high speed air flow) during launch. The fairing is jettisoned when the rocket has reached the upper atmosphere and the aerodynamic forces are no longer significant. When the upper stage has finished firing and is coasting, the upper stage (and satellite) was spun up to 5 rpm prior to release of the satellite. This provides initial stability for the satellite after release from the rocket upper stage. The Ariane 4 put the Intelsat VI satellites directly into a transfer orbit. Ground commands would fire the apogee engines for circularizing of the initial orbit and stabilization at the desired geostationary orbital location. Ground commands would then also be used to command the satellite to spin up to its normal spin rate.

Via U.S. Space Shuttle

When launched by the U.S. Space Shuttle a solid propellant perigee stage (motor and carrier) would be attached to the bottom of the spacecraft. This carrier was used to mount the satellite into a cradle in the Space Shuttle cargo bay. The satellite was ejected from the space shuttle "Frisbee-style" which imparted a stabilizing spin to the satellite. The satellite was allowed to drift a safe distance from the space shuttle before the perigee motor was fired. [2] The perigee motor provided energy (velocity) to the satellite to raise the apogee of the satellite's orbit; it is named for the location in the orbit at which it is used. The perigee motor was jettisoned after it was used. The liquid fuel apogee engines of the Intelsat VI satellites were then used to boost the perigee of the satellite and provide orbit circularization through apogee burns.

On station

Upon arrival on station (assigned geostationary orbital location) and after correct orientation, the payload (and antenna) section of the satellite would be de-spun and pointed at the desired location on the earth, the solar array would be deployed, and the communications antenna would be deployed.

Intelsat 603

Intelsat 603 was launched by a Commercial Titan III on 14 March 1990. The separation of the upper (second) stage from the satellite failed. [3] This left the satellite and the upper stage attached to each other, and Intelsat was unable to fire the perigee motor to boost the satellite to its higher orbit. Intelsat flight controllers jettisoned the perigee motor which detached the satellite from the Titan upper stage. However without the perigee motor the satellite could not be boosted to its nominal geostationary orbit. The on-board propulsion system was used to move the satellite into a slightly higher stable orbit.

Intelsat arranged for a rescue of 603 by the US Space Shuttle. STS-49 was launched on May 7, 1992, 7:40 p.m. EDT. Three of the shuttle astronauts successfully captured the satellite by hand on May 14, 1992, after several failed attempts using a capture bar. After being secured in the shuttle cargo bay, a new perigee kick motor was installed. Intelsat 603 was released from the shuttle and the perigee kick motor was successfully ignited and 603 was placed into the proper geostationary orbit.

Intelsat VI Model

A 1/2 scale model is on display in the main lobby of the Intelsat Headquarters building, which is located at 3400 International Drive NW, Washington DC 20008. There are other Intelsat satellites models displayed, along with models of several rockets that have been used to launch Intelsat satellites.

Related Research Articles

Syncom started as a 1961 NASA program for active geosynchronous communication satellites, all of which were developed and manufactured by the Space and Communications division of Hughes Aircraft Company. Syncom 2, launched in 1963, was the world's first geosynchronous communications satellite. Syncom 3, launched in 1964, was the world's first geostationary satellite.

<span class="mw-page-title-main">Geostationary transfer orbit</span> Hohmann transfer orbit used to reach geosynchronous or geostationary orbit

A geostationary transfer orbit (GTO) or geosynchronous transfer orbit is a type of geocentric orbit. Satellites that are destined for geosynchronous (GSO) or geostationary orbit (GEO) are (almost) always put into a GTO as an intermediate step for reaching their final orbit.

The design of spacecraft covers a broad area, including the design of both robotic spacecraft, and spacecraft for human spaceflight.

AMOS-1, then INTELSAT 24, is a commercial communications satellite which was operated by Spacecom as AMOS-1, for Affordable Modular Optimized Satellite and formed part of the AMOS series of satellites. It was the first Israeli civilian communications satellite, and was initially positioned at 4° West longitude in geostationary orbit. Then in September 2011, it was moved to 31° East.

<span class="mw-page-title-main">Alphabus</span>

Alphabus is a family of heavy geostationary communications satellites developed by a joint venture between Thales Alenia Space and EADS Astrium Satellites in France, with support of the Centre national d'études spatiales (CNES), the French space agency and the European Space Agency (ESA).

<span class="mw-page-title-main">Intelsat 603</span> Geostationary communications satellite

Intelsat 603 or IS-603, previously named Intelsat VI F-3, is a communications satellite operated by Intelsat. Launched in 1990, it was the second of five Intelsat VI satellites to be launched. The Intelsat VI series was constructed by Hughes Aircraft, based on the HS-389 satellite bus.

Intelsat 19 is a geostationary communications satellite operated by Intelsat. It was constructed by Space Systems/Loral, based on the LS-1300 satellite bus. It was successfully launched by Sea Launch using a Zenit-3SL launch vehicle on 1 June 2012 at 05:22:59 UTC. Upon entering service it replaced Intelsat 8 at 166° East Longitude.

<span class="mw-page-title-main">INSAT-1B</span>

INSAT-1B was an Indian communications satellite which formed part of the Indian National Satellite System. Launched in 1983, it was operated in geostationary orbit at a longitude of 74 degrees east. At the end of its seven-year design life it was replaced by the newly launched INSAT-1D, dropping to backup status. In 1992, it was relocated to 93° east, before being decommissioned in August 1993.

Orion 3 was an American spacecraft which was intended for use by Orion Network Systems, as a geostationary communications satellite. It was to have been positioned in geostationary orbit at a longitude of 139° East, from where it was to have provided communications services to Asia and Oceania. Due to a malfunction during launch, it was instead delivered to a useless low Earth orbit.

Intelsat 15, also known as IS-15, is a communications satellite owned by Intelsat. Intelsat 15 was built by Orbital Sciences Corporation, on a Star-2.4. It is located at 85° E longitude on the geostationary orbit. It was launched from Baikonur Cosmodrome to a geosynchronous transfer orbit on 30 November 2009 by a Zenit-3SLB launch vehicle. It has 22 active Ku band transponders, plus eight spares. Five of those transponders are owned and operated by SKY Perfect JSAT Group under the name JCSAT-85.

Space Infrastructure Servicing (SIS) is a spacecraft concept being developed by Canadian aerospace firm MDA to operate as a small-scale in-space refueling depot for communication satellites in geosynchronous orbit.

Intelsat 601, previously named Intelsat VI F-1, was a communications satellite operated by Intelsat, and later Europe*Star. Launched in 1991, it was the last of five Intelsat VI satellites to be launched. The Intelsat VI series was constructed by Hughes Aircraft, based on the HS-389 satellite bus.

Intelsat 605, previously named Intelsat VI F-5, was a communications satellite operated by Intelsat. Launched in 1991, it was the fourth of five Intelsat VI satellites to be launched. The Intelsat VI series was constructed by Hughes Aircraft, based on the HS-389 satellite bus.

<span class="mw-page-title-main">Inmarsat-4A F4</span>

Inmarsat-4A F4, also known as Alphasat and Inmarsat-XL, is a large geostationary communications I-4 satellite operated by United Kingdom-based Inmarsat in partnership with the European Space Agency. Launched in 2013, it is used to provide mobile communications to Africa and parts of Europe and Asia.

Intelsat III F-2 was a communications satellite operated by Intelsat. Launched in 1968 it was operated in geostationary orbit at a longitude of 24 degrees west for around eighteen months.

Intelsat III F-3 was a geostationary communications satellite operated by Intelsat. Launched in 1969 it was intended for operations over the Pacific Ocean; however, it spent most of its service life over the Indian Ocean at a longitude of 63 degrees east.

Intelsat 29e, also known as IS-29e was a high throughput (HTS) geostationary communications satellite designed and manufactured by Boeing Satellite Development Center on the BSS 702MP satellite bus. It is the first satellite of the EpicNG service, and covers North America and Latin America from the 50° West longitude, where it replaced Intelsat 1R. It also replaced Intelsat 805 which was moved from 56.5° West to 169° East. It has a mixed C-band, Ku-band and Ka-band payload with all bands featuring wide and the Ku- also featuring spot beams.

Intelsat 802 was a communications satellite operated by Intelsat. Launched in 1997 it was operated in geostationary orbit at a longitude of 174 degrees west for around fourteen years.

NSS-5 is a communications satellite operated by Intelsat and after by SES World Skies. Launched in 1997 it was operated in geostationary orbit at a longitude of 50.5 degrees east for around 14 years.

Intelsat 804 was a communications satellite operated by Intelsat. Launched in 1997 it was operated in geostationary orbit at a longitude of 44 degrees east for around 8 years.

References

  1. ↑ Hughes Aircraft Corporation Space and Communications Group Intelsat V brochure 826421M/20K/10-82
  2. ↑ SBS F6 Prime brochure, Hughes Space and Communications Group 856268/6-85/10M
  3. ↑ "STS-49: The Rescue of INTELSAT-VI". Archived from the original on 2008-12-16. Retrieved 2009-01-04.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.