TDRS-K, built on the 601HP platform, before launch
|First launch||Optus B1 13 August, 1992|
|Last launch||TDRS-M 18 August, 2017|
The Boeing 601 (sometimes referred to as the BSS-601, and previously as the HS-601) is a communications satellite bus designed in 1985 and introduced in 1987 by Hughes Space and Communications Company. It was designed for such applications as direct television broadcasting to small receiving antennas, very small aperture terminals for private business networks and mobile communications. The series was extremely popular in the 1990s, with more than 84 purchased by customers around the world. The more advanced 601HP derivative (for "high power") was introduced in 1995. Hughes, and the 601 platforms, were acquired by Boeing in 2000.
The last commercial 601 satellite was ordered in 2001 and launched in 2004. The NASA Space Communications and Navigation (SCaN) Program Office in December 2007 selected the BSS-601HP for its third generation TDRS spacecraft, adding the two 15-foot (4.5m) diameter steerable antennas. The TDRS-M satellite, launched on August 18, 2017, became the last 601 satellite to reach orbit.
The Boeing-601 model was Hughes’ first major design and development for a communications satellite with three-axis, or body stabilization. All previous Hughes satellite models (HS-376) had been cylindrical spacecraft that were spin-stabilized at 50 revolutions per minute. Design of the Boeing-601 began in 1985, with full-scale development following two years later. The new satellite’s first official public presentation took place at the Telecom 87 conference in Geneva, Switzerland.
Boeing-601HP A high-power version of the standard model Boeing-601, it can carry payloads twice as powerful as the classic Boeing 601 models. Technology innovations since its original 1985 design, in gallium arsenide solar cells, advanced battery technology, and xenon ion propulsion system (XIPS) option facilitated this upgrade. The 601HP can feature as many as 60 transponders and provide up to 10,000 watts. The 601HP made its debut in 1995, with upgrades in 2000 to address design and component failures.
Ultra High Frequency Follow On (UFO) The U.S. Navy began replacing and upgrading its ultra-high frequency (UHF) satellite communications network during the 1990s with a constellation of customized HS-601 satellites known as the UFO (Ultra High Frequency Follow On) series. These satellites support the Navy's global communications network, serving ships at sea and a variety of other U.S. military fixed and mobile terminals. They are compatible with ground- and sea-based terminals already in service. Eleven UFO satellites were launched between 1993 and 2003. The UHF Follow-On constellation replaced the Fleet Satellite Communications (FLTSATCOM) and the Hughes-built Leasat spacecraft.
Geostationary Operational Environmental Satellite system (GOES), operated by NOAA, selected the standard Boeing 601 bus for its third generation weather satellites: GOES-13, GOES-14, GOES-15. This series featured a sun-pointed extreme ultraviolet sensor, a Solar X-Ray Imager (SXI), and space environment monitoring (SEM) instruments for their Space Weather role.
Tracking and Data Relay Satellite (TDRS) The Second generation satellites (3) used the standard 601 bus, while the follow-on Third generation satellites (3) use the 601HP bus, after design changes addressing satellite failures in 1990s. The TDRS version features two 15-foot-diameter steerable graphite composite mesh antennas. These antennas are partially curled-up like a taco shell to fit within the Atlas/Centaur payload fairing.
The 601 bus is divided into two modules. The first module houses the propulsion system, batteries, and electronics for the bus, and bears launch vehicle loads. The second module contains shelves carrying the communications equipment, payload electronics, and heat pipes. Solar arrays, reflectors, and antenna feeds are mounted to the payload module.
Spacecraft Control Processor (SCP)
An unconfirmed number of 601s launched prior to August 1997 have a design flaw in their SCPs, where a tin-plated relay forms crystalline "whiskers" under certain specific conditions. These whiskers eventually caused an electrical short. Each satellite contains two SCPs and the backup unit will take control in the event of a failure of the primary unit. In some cases, both SCPs have failed, rendering the spacecraft unusable. A notable example was the Galaxy IV satellite. At least eight 601s have experienced SCP failures; four of which were double failures resulting in total loss of the satellite. Hughes switched to nickel plating on later 601s to resolve this problem, at the expense of payload weight.
Xenon Ion Propulsion System (XIPS)
Some Boeing-601 satellites featured the optional electronic propulsion system, called Xenon Ion Propulsion System or XIPS, for station keeping. Compared with traditional chemical propulsion systems, this xenon-based system is more efficient. With an XIPS on board, propellant mass on a satellite designed for 12 to 15 years of operations can be reduced by up to 90 percent. Customers using XIPS can either extend satellite life or increase payload capabilities while holding satellite weight constant. At least four satellites with XIPS propulsion have experienced partial or total failure of the XIPS system which significantly reduced the lifespan of the satellite.
Satellites based on the 601 and 601HP
|Current or last operator||Satellites|
|APT Satellite||Apstar 2 (destroyed in launch accident, January 1995)|
|Asia Satellite Telecommunications Company||AsiaSat 3S|
|Indosat||Palapa C1 (launched January 1996)|
Palapa C2 (launched May 1996)
|Intelsat||Intelsat 2 (launched July 1994)|
Intelsat 3R (launched January 1996 as PAS-3R)
Galaxy 4R (601HP; launched April 2000; originally operated by PanAmSat, which was later acquired by Intelsat)
Intelsat 5 (601HP; launched August 1997; known variously as IS-5, PAS-5, and Arabsat 2C)
Intelsat 9 (601HP; launched July 2000 as PAS-9 operated by PanAmSat)
Galaxy 10R (601HP; launched January 2000)
|JSAT Corporation||JCSAT-3 (launched August 1995)|
JCSAT-4 (launched February 1997)
JCSAT-5 (launched December 1997)
JCSAT-4A (launched February 1999; formerly designated JCSAT-6)
JCSAT-8 (launched March 2002)
|Loral Space & Communications||Orion 3 (601HP; launched May 1999; failed to achieve correct orbit)|
|MEASAT||MEASAT-3 (launched December 12, 2006)|
|NASA||TDRS-H (launched June 2000)|
TDRS-I (launched March 2002)
TDRS-J (launched December 2002)
TDRS-K (601HP; launched January 2013)
TDRS-L (601HP; launched January 2014)
TDRS-M (601HP; launched August 2017)
|Optus (formerly AUSSAT)||Optus B1 (launched August 1992)|
Optus B2 (launched December 1992; launch failure)
Optus B3 (launched August 1994)
Galaxy VIR (601HP)
Galaxy VIIIi (601HP)
Galaxy X (601HP)
Galaxy XR (601HP)
PAS-2 (launched July 1994)
PAS-3 (launched December 1994; launch failure)
PAS-3 (spare satellite launched January 1996; re-designated PAS-3)
PAS-4 (launched August 1995)
PAS-5 (601HP, launched August 1997; first 601 HP to launch)
PAS-6B (launched December 1998)
PAS-10 (launched May 2001)
PAS-22 (launched as AsiaSat 3; later sold to Hughes Communications and re-designated HGS-1;
then sold to PanAmSat and re-designated PAS-22)
(formerly ICO Global Communications)
|(Twelve satellites in MEO)|
|Satmex||Solaridad 1 (launched November 1993)|
Solaridad 2 (launched October 1994)
Satmex 5 (601HP; launched December 1998)
|SES S.A.||Astra 1C|
SES-7 (launched May 2009 as ProtoStar 2 for ProtoStar Ltd; later sold to SES)
|SKY Perfect JSAT Group
(formerly Space Communications Corporation)
|Superbird-C (launched July 1997)|
Superbird-B2 (601HP; launched February 2000; previously designated Superbird-4)
Superbird-6 (launched April 2004)
(formerly Motient Corporation,
American Mobile Satellite Corporation)
|AMSC-1 (launched April 1995)|
|TMI Communications||MSAT-1 (launched April 1996)|
|United States Navy||Eleven UHF Follow-On spacecraft designated F1-F11 (launched between 1993 and 2003)|
- "History: 601 Satellite". Boeing. Retrieved 2013-07-12.
- "TDRS-M Satellite Overview". Spaceflight101.com. Retrieved 18 August 2017.
- "Boeing 601 Fleet". Boeing. Archived from the original on 2013-06-30. Retrieved 2013-07-12.
- "Sat-ND Failures - HS 601 Launch List (incomplete)". Sat-ND. Retrieved 2015-08-23.
- "Boeing 601 Space Systems Forecast – Satellites & Spacecraft". Forecast International. January 2008. Retrieved 18 August 2017.
- Felps, Bruce (1999-05-17). "'Whiskers' Caused Satellite Failure: Galaxy IV Outage Blamed On Interstellar Phenomenon". Wireless Week. Archived from the original on March 3, 2009.
- "Sat-ND Failures - HS 601 SCPs". Sat-ND. Retrieved 2015-08-23.
- "PanAmSat suffers satellite setback". CNET. Retrieved 2015-08-23.
- "PanAmSat Cancels Galaxy 8iR Contract". SPACEandTECH Digest. Retrieved 2015-08-23.[permanent dead link]
- "Sat-ND Failures - XIPS". Sat-ND. Retrieved 2015-08-23.