Re: NROL-38 pre-launch elements

From: Bob Christy (bob@zarya.info)
Date: Sat Jun 16 2012 - 18:59:59 UTC

  • Next message: Ted Molczan: "RE: NROL-38 pre-launch elements"

    If it helps, and you have not factored it in, there is a NOTAM for the 
    upper stage de-orbit:
    
    A2527/12 - AIRSPACE DCC ER OPA6563 ATLAS REENTRY STATIONARY RESERVATION 
    WITHIN AN AREA BNDD BY 1900N/17930E 1530N/16900W 0930N/17100W 
    1300N/17730E. SFC-UNL. 18 JUN 21:14 2012 UNTIL 18 JUN 22:19 2012. 
    CREATED: 16 JUN 01:18 2012
    
    Bob Christy
    
    On 16/06/2012 18:57, Ted Molczan wrote:
    > NROL-38 is scheduled for launch from Cape Canaveral on an Atlas V-401, on 2012 Jun 18, between 12:26 UTC and 13:25 UTC.
    >
    > http://www.spaceflightnow.com/atlas/av023/status.html
    >
    > The launch azimuth indicates that the final orbit will be geosynchronous.
    >
    > The payload probably is an SDS (Satellite Data System) communications satellite. The main purpose of the SDS satellites
    > is to relay data in real-time from the four KeyHole imagery intelligence satellites that operate in low Earth orbit,
    > directly to NRO receiving stations in the U.S.A. The primary SDS constellation consists of two satellites in Molniya
    > orbit and two in GEO. They are often augmented by older spacecraft that remain operational years after their
    > replacements have been launched.
    >
    > Last year, NROL-27 launched USA 227 (11011A / 37377), which replaced SDS 3-1 (00080A / 26635) at 10 deg W; therefore, I
    > expect NROL-38 to replace SDS 3-2 (01046A / 26948) at 144 W.
    >
    > I estimate the following LEO parking orbit, based on launch at window-open. The epoch corresponds to the
    > first-descending node, where GTO burns typically occur:
    >
    >                                                           259 X 272 km
    > 1 79301U          12170.53553244  .00000000  00000-0  00000-0 0    05
    > 2 79301  27.2800 271.6402 0010000 183.0000 359.3500 16.05000000    03
    >
    > 1. GTO at first-descending node
    >
    > If the launch profile is similar to that of NROL-27, and based on the partial elements reported to the U.N., these are
    > the approximate elements of the GTO, assuming the burn occurs at the first-descending node:
    >
    > Descending node GTO                                    269 X 37496 km
    > 1 79301U          12170.53553245  .00000000  00000-0  00000-0 0    06
    > 2 79301  26.5000 271.6349 7368580 182.7760 359.6507  2.16290000    00
    >
    > 2. GTO at first-ascending node
    >
    > Due to the white skin of the Centaur stage of this launch, there is speculation that the launch profile will be of the
    > extended coast type, in which GTO is accomplished using two large manoeuvres separated by more than an hour, resulting
    > in a perigee altitude of at least several thousand kilometres and a significantly lower inclination than usual:
    >
    > http://forum.nasaspaceflight.com/index.php?topic=28559.30
    >
    > I lean toward the possibility of a single GTO burn, but delayed to the first ascending node, which would occur at near
    > 13:35 UTC (MET 01h09m). Allowing for time to complete the burn, spacecraft separation, the Centaur's CCAM (collision and
    > contamination avoidance manoeuvre) and fuel dump, could extend the Centaur's period of operation to more than 2 hours. I
    > do not know whether that is sufficient to require the thermal paint.
    >
    > Here is the ascending-node burn version of the above GTO TLE:
    >
    > Ascending node GTO                                        269 X 37496
    > 1 79301U          12170.56621946  .00000000  00000-0  00000-0 0    03
    > 2 79301  26.5000 271.4034 7368580   0.0000   0.0000  2.16290000    03
    >
    > My confidence that this is an SDS launch is 90 percent; to be certain, we will have to see where it goes, and what it
    > does.
    >
    > It should not be difficult for experienced observers to find the payload if/when it arrives at the 144 W SDS slot. Its
    > initial operational inclination is likely to be about 5 deg.
    >
    > Greg Roberts has reported 27 brightness observations of USA 227 during 10 sessions, which indicate standard visual
    > magnitude similar to the 3rd generation SDS: about magnitude 3.5 (1000km range, 90 deg phase angle). As additional
    > brightness observations accumulate, it may become possible to discern whether the USA 227 and later launches employ the
    > same bus as the 3rd generation. (My guess is that they are different.)
    >
    > Happy hunting!
    > Ted Molczan
    >
    >
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