Syncom IV (Leasat) Syncom

syncom iv, hughes owned military leasat

the 5 satellites of 1980s leasat (leased satellite) program (leasat f1 through leasat f5) alternatively named syncom iv-1 syncom iv-5 , called hs 381 manufacturer. these satellites considerably larger syncoms 1 3, weighing 1.3 tonnes each (over 7 tonnes launch fuel). @ 4.26 meters (14.0 ft), satellites first designed launch space shuttle payload bay, , deployed frisbee. satellites 30 rpm spin-stabilized despun communications , antenna section. made solid rocket motor initial perigee burn , hydrazine propellant station keeping , spin stabilization. communications systems offers wideband uhf channel (500 khz bandwidth), 6 relay 25 khz channels, , 5 narrowband 5 khz channels. in addition fleet broadcast frequency, in military s x-band. system used military customers in , later in australia. of satellites retired in 1990s, 1 remain operational until 2015. during first gulf war, leasat used personal communications between secretary of state james baker , president george h. w. bush, more typically used mobile air, surface, subsurface, , fixed earth stations of navy, marine corps, air force, , army.

hughes contracted provide worldwide communications system based on 4 satellites, 1 on continental united states (conus), , 1 each on atlantic, pacific, , indian oceans, spaced 90 degrees apart. 5 satellites ordered, 1 replacement. part of contract associated control systems , ground stations. lease contracts typically 5-year terms, lessee having opportunity extend lease or purchase equipment outright. navy original lessee.

leasat f1 s launch cancelled prior lift-off, , f2 became first orbit on august 30, 1984 aboard discovery on shuttle mission sts-41-d. f2 largely successful, wideband receiver out of commission after 4 months. f1 launched on november 8, 1984 aboard sts-51-a. followed on april 12, 1985 leasat f3 on sts-51-d. f3 s launch declared failure when satellite failed start maneuver geostationary orbit once released discovery. attempts shuttle astronauts activate f3 makeshift flyswatter unsuccessful. satellite left in low earth orbit, , space shuttle returned earth. failure made front page news in new york times. hughes had insurance policy on satellite, , claimed total loss spacecraft of $200 million, amount underwritten numerous parties.

however, satellite planned launched, determined space walk subsequent shuttle crew might able wake craft. best guess switch had failed turn on satellite. bypass box hastily constructed, nasa excited offer assistance, customer supportive, , insurance underwriters agreed fund attempt @ space salvage – first.

on august 27, 1985 discovery again used launch leasat f4, , during same mission (sts-51-i) captured 15,000 lb stricken f3. astronaut james van hoften grappled , manually spun down f3 satellite. after bypass box installed van hoften , bill fisher, van hoften manually spun satellite up. once released, f3 powered up, fired perigee motor , obtained geostationary orbit. (this scenario play out again in 1992 intelsat 603 , endeavour.) while f3 operational, leasat f4 failed , declared loss after 40 hours of rf communications.

the stricken f4 did not remain complete failure. data f4 s failure permitted saving of f1 premature failure. since of leasats spin-stabilized, have bearing point connects non-rotating , rotating parts of spacecraft. after f4 s communication failure, suffered spin lock while attempting jostle communications payload: spun , despun sections locked together. remembering second failure of f4, , f1 beginning wear out @ spin bearing, decided flip f1 every 6 months keep payload in sun. f1 went on operate smoothly remaining life , never encountered locked despun section.

leasat f4 subsequently powered down , moved graveyard orbit large amount of station keeping fuel in reserve. fortuitous; when satellite suffered loss of fuel ten years later, hughes engineers pioneered use of alternative propellants leasat f4. long after primary mission had failed, f4 powered on test whether satellite kept on station using nonvolatile propellants. f4 used perform numerous tests, including maneuvers oxidizer propulsion once hydrazine ran out.

the fifth , last leasat (f5), built spare, launched columbia mission sts-32 on january 9, 1990. last active leasat, officially decommissioned on september 24, 2015, @ 18:25:13 utc. f5 1 of longest-serving , successful commercial satellites. towards end of 25-year life, f5 had been leased australian defence force uhf service.