NROL-76 is scheduled for launch from Cape Canaveral on a Falcon 9 v1.2, during a two hour window that opens on 2017 May 01 at 11:00 UTC. https://spaceflightnow.com/2017/04/29/nrol-76-mission-status-center/ Based on the quoted report below, I now believe that the payload may be an imagery intelligence satellite built by Ball Aerospace. https://spaceflightnow.com/2017/04/30/spacex-launch-scrubbed-in-final-minute-of-countdown/ "An NRO spokesperson said Sunday that a commercial company, Ball Aerospace, booked the launch with SpaceX as part of a "delivery in orbit" contract with the NRO. Delivery in orbit typically describes an arrangement where a spacecraft manufacturer - in this case, apparently Boulder, Colorado-based Ball Aerospace - is in charge of all satellite preparations, the launch and in-orbit testing, before handing over control of the payload to the end user once it is operational in space." Ball's BCP 5000 bus seems relevant here: http://www.ball.com/aerospace/Aerospace/media/Aerospace/Downloads/BCP_SC_0916.pdf?ext=.pdf "Our BCP-5000 offers our highest performance, most capable spacecraft - DigitalGlobe's choice for WorldView-1, -2 and -3 space vehicles. This powerful spacecraft accommodates next-generation optical and synthetic aperture radar remote-sensing payloads. The BCP-5000 provides increased power in standard increments; higher agility with control moment gyros (CMGs) - providing rapid retargeting capability with stability for the finest-spatial-resolution payloads. The BCP-5000 is the quintessential choice for firm, fixed-priced spacecraft missions." An SAR version would make sense in a 50-60 deg orbit. This might well be the replacement or follow-on of USA 193. USA 193 was the payload of NROL-21. It failed shortly after it reached orbit in December 2006. If NROL-76 enters an orbit similar to that of USA 193, the it would have approximately the following elements, assuming launch at 11:00 UTC. USA 193 replacement 353 X 366 km 1 74301U 17121.59266207 .00000000 00000-0 00000-0 0 07 2 74301 58.5000 286.8357 0010000 90.2000 319.8000 15.69650000 09 Stage 2 after de-orbit burn 59 X 365 km 1 74302U 17121.59266208 .00000000 00000-0 00000-0 0 09 2 74302 49.5000 271.4447 0232000 258.5002 159.5706 16.23000000 09 The epoch is for the time of the stage 2 de-orbit manoeuvre, which includes a plane change to align with the de-orbit zone. The delta-V would be about 2.045 km/s, mainly due to the plane change, which I believe would be feasible because of the large performance margin of the launch vehicle. If NROL-76 is built on the BCP-5000 bus, then its mass may be similar to that of the Worldview satellites, about 2,800 kg. The following estimate shows that this is a fraction of the performance of the Falcon 9 to a USA 193 orbit: http://www.silverbirdastronautics.com/LVperform.html Launch Vehicle: Falcon 9 v1.2 (land recovery) w/standard fairing Launch Site: Cape Canaveral / KSC Destination Orbit: 353 x 366 km, 58.5 deg Estimated Payload: 10927 kg 95% Confidence Interval: 9515 - 12495 kg Note: Caution: limited technical data available Note: Possible dogleg ascent - performance impact estimated As an alternative to a USA 193 orbit, I offer elements of a 50 deg, 300 km orbit. Payload 300 X 306 km 1 74200U 17121.46250000 .00000000 00000-0 00000-0 0 05 2 74200 50.0000 279.9856 0005000 177.0000 220.5000 15.90000000 00 Ted Molczan _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Mon May 01 2017 - 00:13:47 UTC
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