LEASAT F5, The Final Chapter-Andy Ott

INTRODUCTION

Leasat F5 was retired (de-orbited) September 24, 2015. It is one of the longest life Communications Satellites to provide continuous service to a customer and an income stream to the operator. Only Marisat F2 may have exceeded this. It should be noted Marisat F2 was also built by Hughes; for COMSAT in 1973. Ownership of Marisat F2 was transferred to Lockheed Martin when it bought COMSAT in 2000 and subsequently Intelsat in 2004.

The “Leasat Story” describes activities from contract signing to beginning of service for all 5 launched Leasats. This chapter focuses on the final Leasat (F5) mission from turnover to the customer to end of life. However, the chapter also describes how lessons were learned from the previous 4 Leasat missions and how Leasats were used in “innovative ways”, even after so-called end of life. This chapter provides a summary of significant events during on-orbit operations leading up to Leasat F5 retirement. It also captures anecdotes discussed at the Intelsat Operations Control facility with both current and previous employees involved with the Leasat satellite constellation on-orbit operations and some Hughes individuals key to the success of the Leasat Constellation. The author attempted to minimize any overlap with The Leasat Story also on this blog, but some overlap is necessary for continuity and clarification.

There were hundreds of key employees involved in On-Orbit Operations (Launch – IOT – Customer Service – Rescue) for the Leasat Constellation. It is impossible, and unfair, for the author to single out any of these individuals BUT the author would like to identify some key SCG individuals that supported all 5 Leasat missions from SCG. They were: Pete Goshgarian, Larry Nowak, Andy Ott, Chuck Rubin, Jerry Salvatore, Mike Schecter, Paul Sengstock, Loren Slafer, Bruce Tomei, Larry Watson. The author apologizes for any not named and requests you add a comment to the blog.

CONTRACTUAL

  1. $335 Million lease contract from U.S. Navy to Hughes was signed in 1978 for 5 years of communication service at each of 4 orbital locations. Options were identified for 2 years of service extension and the Navy could purchase the satellites after option exercised.

2. In early 1979, Boris Subbotin realized that the three Leasat frequency plans in the original RFQ (X, Y, and Z) for the four ocean regions did not allow for test after launch of a replacement satellite without disrupting ongoing communications. It would also not have allowed Hughes to lease a channel to other users such as NATO or Australian military anywhere around the world. Boris laid out the rationale and frequencies called the “W” Plan and coordinated with the Navy frequency office in Washington for the new W-plan frequencies, as under the original contract, the Navy did not have rights to use W-Plan frequencies. There were no additional costs to the Navy throughout the life of the contract following this change. Addition of the “W” frequency plan was fortuitous as that plan was ultimately used by Hughes Global Services when they leased capacity to the Australian Defense Force.

  1. Neither the lease nor option to buy was exercised by the Navy for any of the Leasat on-orbit satellites.
  2. Leasat F5 was owned and operated by PanAmSat after Hughes acquired controlling interest in PAS. Hughes Global Services, who had exclusive marketing rights, established a contract with the Australian Defense Force in July 1997 and F5 was relocated from 76 deg EL to 156 deg EL.
  3. U.S. DoD signed a new contract in January 2003. Leasat F5 was relocated from 156 deg EL to 100 deg El and continued to serve Australian Defense Force in addition to U.S. Navy.
  4. Ground TT&C up/down RF facility transferred to Optus’ Perth, Australia teleport in March 2003 after a typhoon destroyed antennas on Guam. Satellite engineering and on-orbit control remained at PAS, Long Beach.
  5. Ownership and control were assumed by Intelsat upon the merger of PAS and Intelsat in 2005. This continued until F5 de-orbit Sept 24, 2015.

 

BACKGROUND

  1. Leasat F5 was the “hanger queen” during construction phase as Hughes did not expect to launch it but built it “just in case” of a launch failure.
  2. The shuttle program was grounded after the Challenger disaster in 1986, which allowed additional time to study Leasat F1, F2, F3 and F4 on-orbit performance and take appropriate action on F5 as necessary.
  3. As described in the “Leasat Story”, there were significant on-orbit problems of earlier Leasats prior to F5 launch, so priorities within Hughes were changed and F5 became an essential part of the Leasat on-orbit fleet.
  4. A significant challenge for Leasat F5 were the many delays caused by the Shuttle program and new safety requirements as a result of the Challenger disaster, which led to significant changes to the Leasat structure to provide additional “margin required by NASA” and all NASA documentation had to be updated. Many key employees at Hughes as well as NASA were transferred to other projects.
  5. Bottom Line: Leasat program met and exceeded U.S. Navy requirements and the Navy did not incur any additional costs over the original contract. There was a seamless transition to the UHF Follow On program.

LEASAT FLEET ON-ORBIT SUMMARY OF KEY EVENTS PRIOR TO LEASAT F5 LAUNCH

F2 Launch 8/30/84 (STS41-D)

  1. F2 was launched first because of a concern that F1 had undergone “Protoflight” level testing.
  2. F2 did not have on-orbit problems except the prime and redundant Wideband Receivers failed after only 4 months on orbit. F2 met and exceeded all performance requirements except as noted here.
  3. Seamless planned transition to UHF Follow On satellites.

F1 Launch 11/8/84 (STS51-A

  1. Leasat F1 “Eternal Summer” – explained under F4 Launch.
  2. Seamless planned transition to UHF Follow On satellites.

F3 Launch 4/12/85 (STS51-D)

  1. Failure to activate upon shuttle deployment resulted in 6 months of unpowered exposure to eclipses and full sunlight resulting in all propellants and all batteries freezing. In addition, all units and parts of the spacecraft exceeded their qualification levels substantially. See Leasat Story for more detailed discussion.
  2. Orbit raising resumed after 5 months of unplanned shuttle low orbit (160 nmi) operations. All Propulsion activities performed nominally in spite of the solid and liquid propellants frozen during this time period.
  3. In spite of significantly exceeding qual levels, F3 batteries performed flawlessly, including best life projections at that time of the entire Leasat satellite constellation.
  4. All payload and bus units turned on and performed their function in spite of multiple thermal exposures above qual levels.

F4 Launch 8/27/85 (STS51-I)

F4 failed after 40 hours of full power communications operation (see Leasat Story for details).

  1. Turned F4 on again after several years of no power, in graveyard orbit. All Bus units turned on properly and performed a special test for JCSat described later in the Anecdotes section of this chapter.
  2. When F4 payload completely failed after 40 hours of full RF power operation, initial suspicion was that there could be an intermittent in the UHF multiplexer to antenna output chain. An attempt was made to “rock” the spacecraft which resulted in the spun and despun sections locking together. Subsequent ground testing revealed the likely cause to be a spun barrier splice chip that “potato chipped”, causing interference between spun and despun sections. When F1, after several years in orbit, began to show a gradual increase in friction, experience on F4 resulted in the decision to flip F1 twice a year to keep the sun always facing the payload, essentially putting the spacecraft into “eternal summer”. Jerry Salvatore invented and directed this maneuver for the first year and it worked until end of life. Thus Leasat F4 experience “saved” F1 on-orbit from a potential eventual lockup.

LEASAT F5 TIMELINE

  1. Launch January 9, 1990.
  2. Deployment from the Shuttle 1/9/1990 nominal.
  3. Orbit raising using Leasat Integral Propulsion nominal.
  4. On-Orbit Bus and Payload Test all successful.
  5. Reached contractual 5 year in-orbit service for U.S. Navy.
  6. U.S. Navy exercised option for 2 more years of leased service.
  7. UHF payload capacity reverted to PanAmSat (previously acquired by Hughes) after Navy declined buy-out option. Hughes Global Services (HGS) held exclusive marketing rights.
  8. The Australian Defense Force started out leasing one 5KHz channel and grew to four 5 kHz channels and one 25KHz channel. The U.S. DoD leased various quantities of 25 KHZ channels over the extended life of F5.
  9. There was a plan to de-orbit F5 in 1997, but HGS stood up and said not to just a few hours before planned de-orbit operation.
  10. Ground TT&C up/down-link facility moved to Optus’ Perth Australia teleport after a typhoon destroyed antennas on Guam in March 2003. F5 operations remained with PAS in Long Beach.
  11. Intelsat took control of F5 upon merger of PAS and Intelsat in 2005, and maintained it until de-orbit.
  12. Leasat F5 de-orbited September 24, 2015 to 218 nmi above synchronous

SOME ANECDOTES ILLUSTRATING LEASAT CONSTELLATION OPERATIONS

(In no particular order) (Author noted at end of anecdote)

  1. About the time the first bombing runs began during the First Gulf War, the Navy realized they had valuable national security assets operated in a building that didn’t even have armed security guards.  At the time HCI was located in Buildings S66 and S67.  Being mindful of their assets, they offered to station a couple of squads of armed Marines at the doors.  Fearing that the sight of heavily armed soldiers might tend to drive away highly lucrative commercial business that HCI was enjoying, HCI management wisely said, “Thank you, but no.” And nothing untoward ever did happen as a result of either Gulf War.

(Ken Munson)

  1. Under normal operating instructions from the Navy, if anything happened to a Leasat spacecraft, Operations were supposed to contact the Navy before proceeding with recovery (e.g., switching communications units to redundant, etc).  After the Iraqi invasion of Kuwait, we received different orders.  On the active Leasat spacecraft we were told to monitor certain channels and, if anything at all happened to them, we were to immediately switch to a backup unit and contact the Navy while the recovery was in progress.  Luckily, the channels never had an issue throughout the course of the First Gulf War.  Only after it was all over were we told the reason for the priority of the response.  During the intense negotiations leading up to the formation of the Coalition, those particular channels on the Leasat satellites were the private, high-priority link between Secretary of State Baker and President Bush.  They were in virtually constant contact over the Leasat system as Secretary Baker traveled all over the Middle East to negotiate the building of the Coalition.

(Ken Munson)

3. During both Gulf wars and more recently, ground troops were provided backpacks that had electronics and antenna to be able to communicate with Navy personnel as well as other ground soldiers through Leasat.

(A.O.)

4. “LEASAT was the first commercial communication satellite, perhaps the first satellite, to utilize an on board computer for most of its ACS functions. This processor performed all functions except the de-spin controller.  Since flight qualified microprocessors didn’t exist at the time of the ACS unit design in 1979, the processor was implemented by George Dzeguze using 4 bit arithmetic logic units (ALU), a 12 bit program sequencer, and a handful of TTL logic chips.  The processor multiplied by repetitive addition and shifting, and division was only possible by powers of two using right shift.  All on board computer functions were programmed using 4K words of program memory and 1K bytes of RAM.

(Pete Goshgarian)

5. Due to failure of both Leasat F2 prime and redundant Wideband Receivers after only 4 months on-orbit, a complete rework of one and a complete brand-new build of another was accomplished at Fullerton and installed on Leasat F5. The prime F5 wideband receiver failed after 10 years of service and the new redundant wideband receiver was still operational to F5 de-orbit 25 years later.

(A.O., Rick Mullikin)

6. The 100+ kHz bandwidth relay channel exceeded it’s design life but failed, both prime and redundant, by 2004 (14 years). The 5 and 25 kHz channels were functioning at de-orbit, as well as all bus units, including significant exceedance of all unit and mechanical qual levels as discussed later.

(Rick Mullikin)

7. We had our first confrontation during the F1 launch when we sent 3 up and were trying to recover 2 down (Westar 6 & Palapa B2) with the STS. You didn’t think I was focused on F1.You didn’t understand that I spent 9 months to facilitate a space miracle.

(Jerry Salvatore)

8. When F3 failed to turn on, NASA and Hughes ingenuity responded to define a mission with confidence, based on the recovery/return of 2 satellites the previous year. This was the first and only real time firing of a perigee stage in history.

(Jerry Salvatore.)

  1. After the Challenger disaster in early 1986, NASA would not allow any commercial vehicle launched with the STS. F5 could only be launched on an STS. In 1989, with the STS launches reactivated, NASA had to recover the LDEF (long duration exposure facility) in early 1990 before its unpredictable reentry. Time of liftoff was unpredictable. I proposed the “any time of day launch” for F5. I sold the idea to NASA Houston/Washington, based on the idea that at liftoff, if we couldn’t execute the normal automatic sequence in a normal launch window, we would go to a manual sequence switch before liftoff that would eject the spacecraft with no activity. Based on the experience of the 1984 rescue of Westar6/PalapaB2, we could wait up to 3 weeks to manually initiate the perigee motor sequence and achieve GSO. STS did lift off in the F5 nominal window so F5 was launched like its previous 4 brothers!

(Jerry Salvatore)

10. About 1995 a JCSAT HS393 spacecraft had a piece of debris get stuck in a thruster valve during a stationkeeping maneuver. Over the next several hours, the fuel drained out, leaving it with Oxidizer and a little helium as the only propellant.  The urgency was on to determine if Oxidizer only maneuvers were feasible and what sort of performance could be achieved. Leasat F4, broken and discarded, again came to the rescue!

Using an orbit that was by then several years old and projecting it forward, we were able to relocate the de-orbited Leasat F4 and it responded immediately to commands.  After being cold and dark for several years, all Bus operating units came online and behaved normally.  Working with Loren Slafer, we did a series of big maneuvers to burn through most of the remaining propellants.  At the time F4 was de-orbited, it hadn’t been a requirement to deplete all pressurants so there was still quite a bit left.  It took several hours over a few days to drive the tanks to near depletion.

The propulsion department initiated tests to define what impulse was available with oxidizer or fuel only pulsing. Jerry Salvatore and several Hughes personnel spent 6 months in Japan during late 1997 demonstrating what oxidizer only thruster operations could achieve with 5 and 100 lb thrusters. JCSAT1 was reoriented, relocated and station-kept as a result of these maneuvers. HGS1 was the first HS601 in 1999 that employed the same technique to stationkeep.

Once we got the fuel depletion signature confirmed, we measured the orbit carefully and then began a series of ox-only maneuvers and ranging sessions to measure the effect.  F4 successfully demonstrated the ability to perform ox-only maneuvers on a spinner satellite and to be able to maintain orbital position and to de-orbit.  While JCSAT might not have had the full life it would have had without the failure, F4 demonstrated the ability of a spacecraft to go well beyond the design margins. Oxidizer only maneuvers have been done many times since that first use…

(Original by Ken Munson, additional contributors: Jerry Salvatore, Chris Cutroneo)

11. The ruggedness of Hughes spacecraft is amazing. Leasat F3 and F4 showed that units could survive long periods of extreme cold and significant thermal gradient from hot to cold and yet survive to function.  This was shown again and again as eclipse after eclipse went cold and dark, and yet units revived again without a failure.

(Several commented on this)

12. Confidence in Hughes Spacecraft ruggedness as a result of (10) above convinced Hughes Global Services that they could operate Palapa C1 after it suffered a battery charge control failure and “went dark” during eclipse. HGS ran the satellite, renamed HGS-3, for 10 years, cold soaking it 88 days per year.

(Mark Skidmore)

13. Those long hours of single-prop maneuvers on Leasat F4 were a benefit to every HS601/HS601HP spacecraft that was de-orbited. There, the requirement had been to deplete all pressurants.  That became difficult with a 3-axis bird compared to a spinner but the Leasat experience provided the guide on performance and detection of the depletion events. Again, Hughes Global Services capitalized on this experience and successfully de-orbited HGS-1, an HS-601 HP, on Helium pressurant after several years of oxidizer-only station-keeping.

(Original by Ken Munson, additional contributor Mark Skidmore)

14. As we were doing the depletion burns on F4, Loren Slafer cautioned that it was very desirable to have the fuel deplete first as it would behave very differently if we had to do fuel-only maneuvers.  He indicated that fuel, unlike ox, would tend to freeze as it exited a thruster without the combustion.  During the PAS2 de-orbits, the oxidizer depleted first.  As we did the fuel-only maneuvers, we began to experience wild swings in momentum that nearly drove the spacecraft completely out of control. It became very apparent that, indeed, fuel was freezing on the dark, shadowed side of the body, either at the thruster or adjacent surfaces, and the boiling off as the sun came around caused torques in unexpected directions.  That memory of a single comment from Loren helped save a very troublesome de-orbit operation as PanAmSat was able to adjust their maneuvers to reduce the fuel freezing incidents.

(Ken Munson)

15. Thinking back on the LEASAT program I still have a question on the F4 problem. After the loss of the entire payload, we fired the 100 lb thrusters and locked up the despun section. The only thing we have control of is the time duration of firing. If we had lost one of these thrusters in normal operation, wouldn’t we have had the same result, i.e., lock up the despun?

(Larry Nowak)

16. LEASAT F5 was the last program I worked on before I retired, culminating a 33-year career at Hughes. Other than Surveyor it was decidedly one of the most significant programs I worked on during my career. The experience gained over the years was most useful to help design, test and launch this last spacecraft. The unit engineers were always helpful in explaining important details on the operation of their units. If you don’t understand how it works, how do you know it is working properly? The fact that this spacecraft worked for so many years is a credit to all that worked on this program and is a milestone that will be hard to match.

(Larry Nowak)

17. The move from 72 EL to 156 EL was done using “tip-burn-tip” approach where most of deltaV was devoted to reducing inclination and the east-west station change came for free. This was a key factor in preserving F5’s life. A PAS orbital analyst (Miro Svetinsky) came up with the approach. He is one of the unsung heroes. For the remainder of F5 life, conventional east-west stationkeeping was employed.

(Mark Skidmore)

18. Spacecraft and payload commanding utilized the same automated procedures that were used for ground system testing and on-orbit for F1 through F4 (Paul’s PROCs). It’s remarkable that HCI/PanAmSat/Intelsat only modified PROCs for F5 for convenience.

(Several Intelsat, PAS, and HCI controllers commented on this)

19. One of the major technical challenges for Leasat was making sure we designed out the potential for Passive Intermodulation Products (PIM). PIM is a phenomenon by which ordinary metal to metal contact (or other nonlinear passive components) in proximity to multicarrier RF transmitters act like mixers that cause the transmit carrier energy to frequency spread and interfere with receivers. All subsystems and mechanical/thermal interfaces needed scrutiny. Leasat set up a PIM Review Board for each spacecraft early in the design phase and the board continued to meet until Leasat F5 completed System Testing on the ground. All Hughes L-Band and low frequency satellite programs, including MSat, UFO, GPSIIF, III and Thuraya, subsequently followed this board structure. The board met with REAs of all subsystems to review both mechanical and thermal interfaces within their responsibility and externally with the structure, including detailed drawing reviews focusing on potential for workmanship errors. The board members with the expertise to evaluate the design from a PIM perspective were Bob Reynolds, Steve Young, and Larry Watson. From original design through Leasat F5 build and test, the PIM Board continually discovered potential PIM issues which we had to design out. These became so frequent; the PIM Review Board had a saying once each new potential PIM source was identified – “It Never Ends”. There were no PIM problems with any Leasat satellites so we can now say “It Never Ends – Ends”.(A.O.)

  1. This is way bigger than just the Hughes story.  It was truly a part of shaping the telecom world we live in today.  How cool.

(Rick Mullikin)

CONCLUDING REMARKS

  1. The Leasat program had significant challenges, twists, and turns from initial contract signing in 1978 through this final act. The Leasat on-orbit fleet significantly exceeded all contractual life requirements and it’s robustness proved to be a benefit to other programs as well. Hughes and everyone associated with Leasat should be proud.
  2. Lessons were learned from Leasat F1 through F4 ground test and on-orbit problem analysis and none of the problems were repeated.
  3. Exceptional team approach, including retirees returning to assist in Mission Operations. All operating divisions stepped up with substantial support including independent “Graybeard” reviews.

 

One thought on “LEASAT F5, The Final Chapter-Andy Ott

  1. A “nit” but (with respect to the discussion of PIMS in paragraph 19 of the subject post which cites the “UFO” program) the UHF F/O transponder frequency plan effectively precluded PIM (passive inter modulation product) vulnerability in the receive bands. The largest inter modulation product falling into the UHF receive band was of the 7th (or 9th) order and too small in magnitude to be significant with respect to uplink signal interference.

    The transmit single carrier frequency plan (evenly spaced, narrow-bandwidth single carrier/channel assignments) transmitted via a solid state, hard-limiting amplifier did, however, result in an active IM (AIM?) inter modulation product issue with a few third order active IM products (coincident in frequency with several of the individual downlink carriers) falling back into the transmit band and degrading downlink signal quality. Consequently, the downlink single carrier frequency plan was modified to avoid the equal frequency spacing among the single carriers so that these third order active IM products fell outside the bandwidth of all single carrier downlink signals.