-167- Captain Enright is DSC Program Project Manager, Defense Communications Agency, Washington, D.C.

Transcription

1 C:.. DSCS PTT TRANSFER by Capt R.E. Enrght Captan Enrght s DSC Program Project Manager, Defense Communcatons Agency, Washngton, D.C. Ths wll be a dscusson on the background and the future of the Defense Satellte Communcatons Program. am gong to gve an ntroducton to our satellte system, where we are and where we are gong. The Defense Satellte Communcatons Program s currently operatng wth what we call the Phase One Satellte. lttle satelltes wth a total power output of three watts. about 100 pounds; they are spn-stablzed. They are very unsophstcated They only wegh They have an oddball shape for an equatoral drftng satellte (Fgure 1), but these were orgnally desgned to go nto polar orbt. We now have 26 of these n orbt, 21 of whch are workng. These satelltes are not controllable; we get beacon telemetry out of them but we can't turn them on, we can't turn them off, and we can't move them. They just drft up there at a rate of about 25 degrees per day. Fgure 2 shows our largest termnal whch s the FSC-9. t was desgned back n the days of SYNCOM and has been converted progressvely snce then. t wll operate wth a Phase One brd or a Phase Two brd. t s qute heavy because of the 60-foot dshes. We have two FSC-9's; one at Camp Roberts, Calforna, the other at Ft. Dx, New Jersey. Fgure 3 shows the MSC-46 whch s the "work horse" of our satellte system. We have 14 of these. Theyhave 40-foot dshes and t s -167-

2 possble to move them. We moved one n a lttle over a week n Asmara, although the tme normally quoted s 30 days. We are n the process of mov- - ng another one from Wldwood, Alaska to Taegu, Korea. The TSC-54 s shown n Fgure 4. t has an 18-foot equvalent an- tenna and s hghly transportable. t can be folded up and put n an arcraft n about two or three hours. We have had them operatng wthn two hours after off-loadng from the arcraft. These can be moved, of course, to anywhere that a C-141 or a C-133 equvalent can operate. 3 Our new generaton satellte s shown n Fgures 5a and 5b. Ths s the Trple-7 brd, our Phase Two satellte, whch s qute a bt more sophs- tcated than the Phase One. t s 9 feet n dameter, about 13 feet tall, and weghs about 1150 pounds. t has two steerable antennas; each has a beam wdth of about two and one-half degrees. The horns n the mddle are the earth coverage mode antennas. The satellte generates about 500 watts. Each of the transmtters s powered by a 20 watt TWT. The actual flux densty put out by those narrow beam antennas rght now exceeds the flux densty allowed by the TU, so t may have to be reduced. Ths could provde, between bg antennas, as many as 1200 voce channels of 5 communcatons. On the other hand, f the earth coverage antennas were dedcated to two arborne termnals wth 32-nch dshes, t would take the entre satellte to communcate one 2400-bt data channel. Ths satellte wll serve for analog communcatons, dgtal data users, and t As wll serve such thngs as the wdeband magery and the Compass Lnk photography beng sent back from Vetnam. Not beng n competton wth 3 the commercal satellte people, we can run many dfferent types of sgnals through t. f we were to acqure the wdeband servces through COMSAT 5 rght now, we would have a hard tme payng the bll. COMSAT s now chargng companes such as T&T and World Comm about $4, per 5 voce channel per month. g j -168-

3 Fgure 6 shows the termnal confguraton whch we have at the present moment and t s a pont-to-pont network. We are not very effcent; North- -r west Cape cannot talk to Kwajalen, Northwest Cape talks to Guam. Sagon talks only to Hawa. Hawa, however, relays to Camp Roberts. The frst two Phase Two satelltes were launched November 2 from the Eastern Test Range, and about eght hours after the launch we had lost both of them. Durng the day, we recovered the seral number 2 satellte. t was a combnaton of software problems (they put the "A" program n the "B" computer) and a hardware fault n the satellte. The second satellte was recovered three days later by analyzng the hardware fault. Rght now the hardware faults are under control; they stll exst but we know how to work around them and at ths moment, they do not cause any sgnfcant decrease n relablty. We exepct to test both satelltes over the Los Angeles area (105 0 W and 115'W) for approxmately 60 days, at whch tme the best of the two satelltes wll be drfted to the west to a poston at E. The other satellte wll be put over the Atlantc at 13 0 W. However, that second satellte wll be subject to addtonal testng through our termnals at Fort Monmouth and Fort Dx. Two of these termnals are tranng models; two of them are engneerng models. Fort Dx s part of the engneerng system but later t wll become the backup termnal for our CONUS East. Fgure 6 shows those stes at whch we now have the PTT capablty, or cesum standards. We have drected all the servces to procure cesum standards for all termnals for two reasons. Frst s the advantage of not havng to fly these standards around the world for calbraton, and second we have n our system a spread spectrum devce whose performance can be mproved by use of these standards

4 Now that the satellte has been descrbed, would lke to dscuss some of ts advantages. We can operate n any sort of a mode wth ths satellte. n other words, we can go from earth coverage to earth coverage, transmt on earth coverage and receve on narrow beam, and vce versa. 3 t has adjustable power output and a secure command and telemetry channel. Our hardware problem s n that secure system but t s under control. Another advantage of ths satellte over our current satelltes s that although t wll be geostatonary, we can reposton t at 30 degrees 5 per day, whch s absolutely lnear. n other words, we can reposton t 30 tmes at 1 per day or 15 tmes at 20 per day. t does not start to break 9 down n lnearty untl you get down to below a tenth of a degree per day n postonng. One reason for ths s that the repostonng devce s a pulse jet type of thruster operatng on hydrazene so one tells t how many pulses to shoot out and t gves the delta V to drft nto varous statons. 3 Also suffcent fuel for the east-west staton keepng and slow repostonng s now on board for seven years vce fve years specfed. Therefore, f everythng else works out as well as the Phase One brds we can have these satelltes around for qute some tme. We can swtch between all of the components 3 wthn the satellte and we can control the gans and we can swtch everythng around and steer these antennas n addton to steerng the satellte. 3 Fgure 7 shows a very hgh performance 60-foot antenna. t s not transportable but t s recoverable. t s desgned so that a crew of rggers can dsmantle t n about two weeks and re-erect n about a month. t s all bolted together, there s no weldng that would have to be done. The only thng that s not recoverable s the concrete foundaton. To accompany ths s a new medum termnal shown n Fgure 8. t uses the same antenna desgn as the AN/TSC -54. n the background you see the electronc van, mantenance and supply van and an operatons van

5 '2w C: The vans for the heavy termnal look just lke the vans for the medum termnal. As a matter of fact, you can see a ppelne comng out that contans the Servo control cable and the RF system. f you put a connector n the mddle you can plug ether antenna nto ether set of electroncs. The basc dfference between the two of them s the degree of redundancy n hghpowered amplfers and n some of the up and down converters. These termnals wll be capable of transmttng as many as ten up channels and recevng twelve down channels, t s very versatle. Durng ths past summer, we conducted a serous study of what the post-1976 satellte would look lke and no sgnfcant break throughs are expected between 1976 and However lookng beyond that we see some very fancy satelltes, possbly usng the hgher ranges - 15, 30, 40 ggahertz regon - and we may have satellte-to-satellte lnk at EHF n the 60 ggahertz regon. Ths s the status of the Defense Satellte Communcatons System that wll one day allow us to transfer tme to all of our major bases around the world. The Navy s developng a famly of shpboard termnals. The Ar Force has developed an advanced development model of an arborne termnal

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15 DSCUSSON trr CAPT ENRGHT: have a queston for Dr. Wnkler. Has anyone gven consderaton to the transfer of tme nternatonally usng 'NTELSTAT. DR. WNKLER:, Yes, n fact we have had several long dscussons wth NTELSAT. t appears, that they would consder transferrng tme, but only at a very hgh dollar cost. Apparently the confguraton and the dedcaton of the varous channels s so fxed that t would cause very severe operatonal problems. wonder f Mr. Gatterer would not have some addtonal nformaton. MR. GATTERER: expect that Dr. Wnkler's conversatons wth NTELSAT are far more recent than any that 've had. 've been n communcaton n the past wth COMSAT, and convnced myself of the feasblty of usng ther system for tme transfers. do agree that t appeared qute expensve unless we made use of thngs that would be free, such as the plot tones themselves. However, for a base band transfer, t s qute expensve. Nonetheless, my expectaton s that the only thng better than Loran-C would be a broadband satellte transfer. The only way that can see to mprove over the good tme-transfer capabltes of Loran -C s by usng NTELSTAT. Therefore my expectaton s that t would take place sometme n the future. Would you agree wth that, Dr. Wnkler? DR. WNKLER: Not qute. consder our mmedate needs n DOD as somewhat more mportant at the moment. feel that the Defense Satellte Communcatons System wll satsfy most of our needs; certanly those whch go to centers of actvtes located n strategc areas. n addton to that, we have a number of precse tme requrements whch are way outsde any conventonal operatonal area and must be satsfed by dfferent means. personally beleve that approaches such as these ndcated by Mr. Easton yesterday, or by Dr. Krshner wll provde a truly worldwde capablty. Possbly an mproved transt satellte wll be provded whch wll allow a one-way dssemnaton of tme to a user wthout any retransmsson of sgnals. also thnk that can be done relatvely cheaply and you get around the complcated second step of dstrbutngtmefrom a ground termnal. n defense applcatons that s less of a problem than to go for nternatonal dstrbuton. have at least one promsng thng n mnd and that s that we may be able to make some tme transfers wth the Brtsh, usng the DSCS, n the not too dstant future. There s another mplcaton, however, and wll come to that later n my talk about the UTC adjustments. That s, at any tme we have to nterface wth nternatonal systems or systems operated by other natons, the queston of whch tme scale s to be used and what knd of an operaton wll be adopted s a very mportant one