Attachment INFORMATION

INFORMATION

LETTER submitted by DIRECTV

INFORMATION

2005-06-13

This document pretains to SAT-STA-20050517-00104 for Special Temporal Authority on a Satellite Space Stations filing.

IBFS_SATSTA2005051700104_438200

                                       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)
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        *       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)
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                          Figure 2. Longitude vs Time
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                           Figure 3. Inclination vs. Time
                                      (5 years)
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                 Figure 4. Apogee and Perigee vs. Time
      M                   7    (5 years)

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       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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