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LETTER submitted by DIRECTV

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2005-06-13

This document pretains to SAT-STA-20050427-00091 for Special Temporal Authority on a Satellite Space Stations filing.

IBFS_SATSTA2005042700091_438198

June13, 2005 DIRECTV RECEIVED Ms. Marlene H. Dortch uN 1 3 2005 Secretary Federal Communications Commission Fedenl Connmicatens Connission 445 12" Street, S.W. Oftect Srermby Washington, DC 20554 Re: DIRECTV Enterprises, Requests for Special TenpP@@OWI@t File No. SAT—ST4—20050414—00083 File No. ST—ST4—20050427—00091 auN 2 0 2005 File No. SAT—ST4—20050517—00104 Poly Brench Dear Ms. Dortch: Intomational Cureau As you may be aware, a Satellite Contral Processor (‘SCP") on an HS6O1 satelite not operated by DIRECTV Enterprises, LLC (‘DIRECTV*) recently experienced an in— orbit fallure. DIRECTV has requested authority to relocate the DIRECTV 1 satellite (also an HS601 design) from 101° W.L. to 72.5° W.L.,to replace the DIRECTV 5 satelite currently providing service into the U.S. from that location.". In order o aid the Commission‘s consideration ofthat application and the two related applications also referenced above, DIRECTV hereby provides additional backeround information on this type of failure and the potental impact to service should such a failure occur. As discussed below, the risk of filure ofthe remaining SCP on DIRECTV 1 is very low and will not be increased by relocation ofthe satelite Background on "Tin Whisker" Failures The early HS6O1 satelites are susceptible to a type ofSCP failure commonty referred to as a "tin whisker" failure, s called because they are caused by the growth ofa pure tin crystal on the SCP input power relay that resembles a whisker. Eight conditions must be present in order for his type of failure to occur: + The plating must be puretin. * There must be physical stress in the tin plating (an imperfection or scratch). See DIRECTV Enerpries, Request forSpecial Temporary Authorty, File No.SAT—STA—20050427« goos1 (iled Apr. 27, 2005) ar2e tesr rmeerian wey ti degeness cA sexer rhone srocsancsese x uaiv at tee erntery grveps ine

* There must be a large current source available. * The SCP must be in a vacuum. + The input power relay case must be grounded. * The conformal coating (insulation) on the relay terminals must have voids or be absent * The whisker must grow to a sufficient length. + The whisker must grow in trightdirection. The first four conditions exist in all cases, as they are part ofhe basic design of the satelite. Afer the problem had been diagnosed, inspections ofunlaunched units indicated that 70%6 ofthe relays were grounded (condition 5). Ifthelastthree conditions also exist, the failure propagates as follows: Fizst, a tin whisker grows on the outside of the tin—plated relay case. Next,the whisker bridges the gap between the grounded case and an energized bus power relay terminal that lacks the conformal coat, creating a short circuit At the inception ofthe short, the tin vaporizes and creates a localized plasma that can support large current, which in tum eauses the power supply fuse to blow. Once the fuse has blown, the SCP has no primary power available and becomes non—operational Once this process became well understood, tin plating was eliminated on later models. In addition, several operators,including DIRECTV, now perform annual tests ofthe non— active SCPs on their in—orbit satelites. These tests have never uncovered a failed SCP. To date, itis believed that 10 of the possible 44 SCPs (%e., 23%) in orbit have failed as a result ofthis phenomenon. DIRECTV currently operates only two satellites potentially susceptible to such failire: DIRECTV 1, which previously experienced such a failure, and DIRECTV 2, which has not. The primary SCP on DIRECTV 1 failed on July 5, 1998, afte4.5 years in orbit. Since that time, the satelite has continued to operate nominally using ts bacleup SCP, and it is expected to continue to operate untl the end ofts nominal fuel life several years from now. Since whisker length and growth are time—based phenomena,a model was constructed in order to provide some possible statistical indications offilure probability as a function oftime. That model and the underlying data have been presented to the

FCC previously and, in summary, there seemed to e good correlation between the Iaunch date of thsatellte and the number of years untl an SCP failed in orbi. Specifically, the data indicate that the median time tofailureis approximately 5.5 years and that the mean ime t failure is 6.2 years with a standard deviation o2.6 yeas. Notabl, the latest (non—DIRECTV) failure occurred at 12.70 years nto the satelite‘s lif, oat2.50 standard deviations ofthe mean, meaning that 98.76% ofall failures will occur before thistime if the modelis correct. Sincethe most recent filure is the tenth failure, it is still within the bounds ofthe model (0.55 failures out ofthe 44 would have been expected atthistime period, although, obviously, a partial falure cannot cccur). Ifthe most recent failureis excluded from the model, it would have occurred at 5.5 standard deviations, or essentially outside the previous data. This means that the most recent failure is the extreme event predicted by the current model. Put another way, ifanother failure occurs on a satelite ofsimilar age, another model will have to be developed which encompasses a bi—modal failure distribution. This has implications for DIRECTV 1 (11.5 years on orbit). The longer an SCP remains operating pastthe citial in—orbit ime, the lower is chances of failing in the future, Assuming continued validity ofthe current model, DIRECTV 1 is well past the point where filure should be expected, although there always remains a remote possibility ofanother filure. In any event, DIRECTV has no evidence that would suggestthat stellite location or maneavering ofthe satelite increases thrisk of an SCP failure in any way. Thus, we believe that the recent tin whisker failure ofa non—DIRECTV satellite should have no impact on DIRECTV‘s pending STA request. Impact on Service Ifboth SCPs on a satelite become disabled, it is no longer possible to control the satelite positon. Figures 1 through 4 show the change in orbit longitude (east—west) and inclination (north—south) and apogee/perigee (radial) over time for such a case, assurming the failure occurred at 72.5 WL. The possiblity ofcontact with another satelite diminishes over time.. Figure 2, which is an expansion ofthe data in Figure 1, shows that although the eccentricity and therefore east—west longitudinal movement begins immediately,the satelite i stl within the 0.05 degree station keeping constraints shown by the horizontal lines for about three weeks. This,interestingly, is one advantage of moving a satellte susceptible to SCP filure away from a crowded orbit positin such as 101° WL, where six satelites currently operate. As Figure 3 depicts, he inclination of the orbitis also growing linearly atabout one degree per year and the apogee and perigee * See Leterfrom Hemy Goldbery to MarleneH. Dortch, FCC File No.SAT—STA—20030324.00089 (dred Apei 24,2003)

also diverge from synchronous as shown in Figure 4. ‘The three measures ofposition (east—west, morth—south, and radial) all diverge from the geosynchronous are, and although the satelite will pass through the equatorial plane,the crossings are displaced from the geosynchronous are. This is somewhat analogous to a satelite in transfer orbit passing through the equatorial plane. Therefore, although the satelite would remain near the geosynchronous are, it is clear that as time passes the chance ofcontact with another satelite diminishes. Figure 1. Longitude vs. Time (5 years) wo tessirn e en m vis wme same mam woe wes ww wos en ie ue on

Figure 2. Longitude vs Time Ssd ___—_—(GWeSK§)—_____.__ tegneern mrd m mei sns ares po saies sme mes wase Figure 3. Inclination vs. Time (5 years) } Crnere T wins ns ie nime oo maer we o n mt ww on

Figure 4. Apogee and Perigee vs. Time M 7 (5 years) i masin nasaned w wiee ns wwnme amer sower mm wsnn mm owe o at Although not susceptible to ‘tin whisker" SCP failures because it is based on a different design, DIRECTV 6 has experienced a large number of solar aray failures since its launch in March 1997. Because ofthis, DIRECTV chose to place the stellite where it was authorized to operate on the fewest DBS channels (3),in order to minimize the power requirements and thereby extend the useable lifetime ofthe satelite. As it now stands, DIRECTV 6 can withstand one more filure on each ofthe North and South power busses before DIRECTV will be required to reduce power or tum offtransponders. In addition, DIRECTV anticipates that the satelite will ran out offuel in July 2007. This is why DIRECTV requested authority to relocate DIRECTV 5, which has no power failures, is not an HS6O1 design, and has greater than 10 years oflife remaining, from 72.5° WL to 110° WL" DIRECTV 1 would replace DIRECTV 5 at 72.5° WL. An alterative move ofDIRECTV 1 to 110° WL to replace DIRECTV 6 is possible, but such a move would eliminate service from 110° WL for subscribers in Hawaii and most of Alaska due to the coverage limitations of DIRECTV 1, and therefore that alternative was not considered further. In the event ofa failure or de—orbit ofDIRECTV 6 before a replacement arrives (for example, because DIRECTV 5 is not relieved at 72.5° WL}, 8 See DIRECTV Enterpries, Requestfor Specil Temporary Autoriy,e No. SATSTA— 20050817—00104 (bled May17,2005)

consumers throughout all fify states will be deprived ofthree transponders ofhigh— definition programming, roughly seven channels ofprogramming using current compression technology. x kc % 1 am filing a copy ofthisletter in each ofthe above—captioned files. Please contact me if you have any questions, Sincerely, DIRECTV Enterprises, LC


Document Created: 2005-06-21 15:19:47
Document Modified: 2005-06-21 15:19:47
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