USSTRATCOM has catalogued 56 new pieces of debris from the weather satellite DMSP B5D2-6 (91082A / 21798). They span 1991-082F / 28294 to 1991-082BN / 28349. No elements are available, and none are likely to be published. Hobbyists are the only public source of orbital elements of this object. The last pre-break-up elset is of epoch 2004 Apr 14: DMSP B5D2-6 6.4 1.7 0.0 6.6 v 5.43 1 21798U 91082A 04105.69574099 .00000150 00000-0 76795-4 0 03 2 21798 98.6774 128.2477 0011500 16.4304 343.5695 14.15516896 07 On 2004 May 03 UTC, Paul Gabriel observed 91082A or a related object near the predicted path of 91082A: http://satobs.org/seesat/May-2004/0018.html It was 24.21 s early, and 0.22 deg off the track predicted by the above elements, taking into account Earth's rotation during 24.21 s. This is a large difference, given that the elements were only 18 d old. The object was 25 deg above the horizon, which is not all that high, so to be 0.22 deg off-track suggests that the break-up may have imparted significant velocity. 91082A's orbit is sun-synchronous, so its visibility window is seasonal - during the Northern and Southern hemispheres' respective winters. Weather permitting, it would be worthwhile performing a planar search for debris. I can only speculate as the to the cause of the fragmentation. Shortly after launch, DMSPs (and their NOAA cousins), use hydrazine thrusters to trim their orbit, after which they are made inoperative. Unspent hydrazine has been the cause of numerous satellite fragmentations. I do not recall any other break-ups of DMSPs or NOAAs. The NOAA/DMSP Propulsion and Reaction Control Subsystem is described here: http://www2.ncdc.noaa.gov/docs/klm/html/c1/sec12-3.htm "The hydrazine RCE consists of four thrusters and two spherical storage tanks The hydrazine thrusters are used for maneuvers requiring large control torques and for all velocity change maneuvers, i.e., spacecraft separation from the booster and orbit circulation trim, as well as pitch and yaw control during the AKM burn. After completion of the orbital velocity trim burn, pyrotechnic valves at the outlet of each hydrazine propellant tank may be fired to isolate the hydrazine thrusters from the propellant tanks and render the system inoperative. The cold-gas nitrogen RCE consists of eight thrusters and two spherical storage tanks of usable nitrogen. The nitrogen thrusters are used for three-axis control during ascent (except during AKM burn), Earth acquisition after handover and as a backup for momentum unloading in normal orbit mode control. Four of the thrusters provide roll control through Ascent Guidance Software (AGS), and are operated, under software control, in coupled pairs. The remaining four thrusters are operated individually to provide AGS pitch and AGS yaw control." Ted Molczan ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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