Attachment response

response

REPLY submitted by Northrop

response

2005-05-12

This document pretains to SAT-AMD-20040312-00030 for Amended Filing on a Satellite Space Stations filing.

IBFS_SATAMD2004031200030_434780

Smmen© swuor c amacom eveogs.owcon orecrrn dnerie BY HAND DELIVERY: Ms. Marlene Dortch MaY 1 2 2005 esn CoTmmmsounttateconieCoynnisson Tm Fe deraaltCommunications Commission 445 12® Street, S.W. Washington, DC 20554 Re: Application of Northrop Grumman Space & Mission Systems Corporation, File No SAT—AMD—20040312—00030, Call Sign §2254 Dear Ms. Dortch: Northrop Grumman Space & Mission Systems Corporation ("NGST*), by its attomeys, hereby responds to Te April 27, 2005 letter from Robert Nelson, Chief of the Engineering Branch of the Satellte Dividion of the Commission‘s International Bureau, to Peter Hadinger of NGST ("April 27 Letter®), In the April 27 Letter,the Bureau observes that the orbital parameters of the highty—elliptical orbit ("HEO®)satelites in the non—geostationary satellite orbit ("non—GSO®) component of NGST‘s proposed hybrid Ka—band/V—band non—GSO and geostationary satelite orbit system, as contained in NGST‘s March 12, 2004 amendment (referenced above) are identical to the orbital parameters proposed ten days laterin the amendment of contactMEO Communications, LLC ("contactMBO®) in the latter‘s amendment to is own Ka—band non—GSO satellte system application. April 27 Letter,at 1 & n.1. The Bureau requests NGST to explain the measures it intends to take to avoid in—orbit collisions with respect to the HEO satellitesin the non—GSO component ofthe two proposed systems. It specifically requests that NGST indicate whatsteps have been taken to contact contactMEO and to ascertain the likelihood of successful coordination of physical operations in the event that NGST is relying on physical coordination ofthe two systems 14. ul NGST hereby states thatis does indeed intend to rely on physical coordination of the HEO satelites in the NGST and contactMEO systems‘ non—GSO components at Ka—band. Prior to the filing of NGST‘s own above—referenced amendment in March of 2004, NGST and representatives of contactMEO had a number of discussions that led to the two companies‘ respective decisions to amend their Ka—band non—GSO applications to specify,infer alte, the use of HEO spacecraft with anite s

Ms. Marlene Dortch 4 May 12, 2005 Page —2— identical orbital parameters in the system designs. The ultimate objective was to maximize the companies‘ use ofthe Ka—band non—GSO fixedsatellite service spectrum by ensuring that the separation angle between any two satellites of the two systems as viewed by any earth station of these two systems meets or exceeds the minimum angle required to permit full—time operation by both systems. In the event that both companies are eventually licensed to operate their proposed systems, NGST expects to continue to engage in coordination discussions with contactMEO to ensure that the two systems‘ operations are physically compatible. The commonality of design, and the considerations described below, will contribute greatly to thultimate success of this endeavor. In a nutshell, the fact that the two systems will have identical orbital parameters is not an impediment to successful coordination of physical operations so long as the two systems‘ satelltes are launched on different dates. In both the NGST and contactMeo HEO non—GSO filings, the systems* Right Ascension of the Ascending Node (‘RAAN®) and Mean Anomaly ("MA") are 0/O (Satelite #1, RAAN=0 deg./ MA= 0 deg.), 120/120 (Satelite #2, RAAN=120 deg./MA= 120 deg.) and 2407240 (Satellite #3, RAAN=240 deg./ MA= 240 deg.).‘ These RAANIMA parameters indicate the plane separations of 120 degrees. Even though they will be launched into different initial orbits, in time, when the RAAN of the first satellte drifts around to 0, the others will then be at 120 and 240 RAAN For each system, once launched, the orbit nodes are going to drift westward at a rate of approximately 0.13 degrees per day. This means thatif there is a one—year difference between the launch dates of the NGST HEO satellites and the contactMEO satellites, there would be orbit Right Ascension of the Ascending Node ("RAAN®) separations of some 48 degrees just from the drift of the RAANs. Afterinjection,the orbit RAANs do not stay constant, and there is no orbit maintenance of the RAANs. The 120 degree orbital separation between each system‘s satellites, however, does remain constant. What this means is that despite the fact that the filed orbital parameters of NGSTs and contactMBO‘s HEO non—GSO satellites are identical, operational conditions and coordination between the operators will liminate the potentialfor n—orbit collisions between the systems® sutellites. Specifically: * The NGST RAAN/MA values at the time of Iaunch will be set to provide orbit planes that do not interfere with contacMEO‘s satelltesif the latter‘s satellites have already been launched.® j "The RAANMA values (00, 120/120, 2400240are heintl valuesfo eachsatelitif hy wereto be Inunched on one—monthcenters. The one—month centrsar just anexamplesnce satlite build ate, auncher availablty and range availaility would probably make th time between Inches something olsc . "The RAANMA and dateAime—oF—day combination foreach sateit will be ied t etthe apogee longitude of thesatelites in each HEO system

Ms. Marlene Dortch & May 12, 2005 Page —3— * Though specified as beginning iniial service at approximately the same time, it is extremely unlikely that the NGST and contact MEO system satellites would be launched on the same date due at a minimum to such considerations as booster and range constraints. Ifthe launches occurred on one—month centers (30 days), it would take 5 months to launch a series of six satellites for both systems. * During a sequence of launches, the orbit RAANs of each satellite that has been Iunched would naturally drift at approximately 4 degrees per month (—0.13 deg per day) westward. As a satellt is launched for each system, the orbit RAAN and Mean Anomaly would be adjusted to match up with the previous launches to provide the proper constellation plane separation. In summary, if the satellites were to be launched at approximately the same time of year, he actual launches would be separated in time due to launcher and range constraints. If the launches were to occur on one—month centers, the actual launch RAAN/MAs of each satellite would need to be adjusted to account for RAAN drift since the launch of the first satelite. The resulting orbit planes and orbit positions between the two systems would provide sufficient satellit separation to preclude collisions." At this time, NGST maintains that it would be premature to specify different RAANs for ts satelites to differentiate them from the satellites of contactMEO‘s system, as it is unknown which | 5 An examplesequence of launches for both systems, wth aunches on 30—day mrvals, would produce the followinginital orit RAANs Mort #1 (day 0) System 1, stellte #1, RAAN: 0 deg. Mean anomaly: 0 dex Month #2 (day 30) System 1, stelite #2, RAAN: 116 degrees (120 deg — 194 dep) and Mean anomaly: 128 deg (120 dep + 18 deg)(RAAN adjused o provide proper planeseparaion rom the erbt plan of thepreviouly aunched satelit, MA adjused to placthe satelite on thspecifed system ground tracl) + Month #3 (day 60) System 1, satelite #3,RAAN: 232 degrees 240 deg—2"4 dey), Mean anomaly: 256 degrees 240+ 2"8 dex) "The following lunches ofSystem 2 satelites,withthsame intal RAANsasthe System 1 RAANs,producesan actuslplane eparation from the System 1 steltesdue tthenatural RAAN drifs of heSystem 1 orbit lanesduring thesequence oflaunches. The intiallanes, of each system. ae now separated by 12 degrees(due o natirl RAAN dif oSystem 1), the MA puts the satelite on thesame ground track as System 1 satelftesat a diffrent location ithe orbit o accountfortdiffrent RAANs + Month 4 (day 90System 2,stelite #1, RAAN: 0 degreesand Mean anomaly 24 depres (MA adjusted to provide the same ground track as system 1) + Month S (day 120) System 2, sielite #2, RAAN: 116 degrees(120 194 deg) and Mean anomaly: 152 deg (120 + 24 + 199 dep + Morth 6 (day 190) System 2satlite3, RAAN:232 degrees 240—18 deg) and Mean anomaly: 280 degrees (240 + 24 + 258 deg)

Ms. Marlene Dortch &4 May 12, 2005 Page —4— system will launch first. Even so, on the assumption that both systems will not be launched simultaneously (as explained above), there would be no potential for in—orbit colliions even if the same RAAN/MA combinations are nominally specified in the application. Nevertheless, NGST is prepared, should the Commission so desire, to amend is application to specify altemative nominal RAANs for ts HEO non—GSO satellites. Please inform NGST if additional information on this matteris desized or needed in light of the foregoing discussion. NGST triststhat the Foregoing explanations satisfy the requests the Bureau made in the April 27 Letter. If there are any questions or if any aditional explanation is desired or required, please do not hesitate to contact the undersigned. Respectfully submitted. Artorneyfor Northrop Grumman Space & Mission Systems Corporation ce Mr. Robert Nelson Mr. Kal Krautkramer


Document Created: 2005-05-18 15:55:52
Document Modified: 2005-05-18 15:55:52
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