1988-008B
The Delta 181 mission was flown using the final Delta 3910 rocket, with a TRW-201 engine powering the second stage. The Delta 181 sensor module was built by APL; it remained attached to the McDonnell Douglas Delta stage and the combined spacecraft had a mass of around 2700 kg not including the empty stage. The sensor module had radars, and UV, visible and infrared instruments. The mission was launched in Feb 1988 and designated USA 30. It was used to characterize sensor responses to various ejected test targets, and to measure backgrounds. Although various primary source documents have been declassified, the Aviation Week report remains the most detailed available account of the subsatellite deployments.
The vehicle ejected 14 test objects, mostly 0.6 to 1.0m in size and representing Soviet reentry vehicles and post-boost vehicles. The Science Package 1 group of 6 objects included a sensor calibration reference satellite, and were released into the initial elliptical orbit. An orbit raise burn over Madagascar on the first orbit followed the release. The Science Package 2 release deployed 5 more satellites beginning at the end of the second orbit, over the Pacific. About 4 hours into the flight, according to AWST, a subsatellite was ejected which including test of a small solid rocket motor (I suspect it was closer to T+4:13 when the mission was over Guam). However, AWST also reported that a total of three test objects carried Star 6 motors, so it is not clear if there is anything special about this test object except that it was the last. I have arbitrarily assumed that objects 7 and 9 carry the other two motors. The canister cluster subsatellite, with gas release experiments, was ejected later, followed finally by Science Package X, the Space Plume experiment which was housed underneath the cluster. Its Star 13 motor fired over Maui.
Only 4 objects were cataloged for the mission - A is the canister cluster and B is the Delta/sensor module. C and D have small RCS and are presumably test objects that were not deorbited; C is a group 2 object and D is in the group 1 orbit- it is probably the sensor calibration satellite. The four objects with solid motors probably were deorbited and so their absence from the catalog is expected. The remaining seven satellites, however, would have been expected to remain in orbit. Perhaps their ejection velocities were such as to ensure their immediate reentry.
On rev 8, the vehicle was placed in a circular orbit in gravity gradient orientation for data return.
The spacecraft returned data for two months until reentry.
| Delta 181 | |||
| Date | Time | Event | Orbit |
|---|---|---|---|
| 1988 Feb 8 | 2207:00 | Launch by Delta 3910 | CC LC17B |
| T+1:00 SRM 1-6 out | |||
| T+1:04 SRM 7-9 on | |||
| T+1:05 SRM 1-6 sep | |||
| T+2:04 SRM 7-9 out | |||
| T+2:07 SRM 7-9 sep | |||
| T+3:43 MECO | |||
| T+3:49 VECO | |||
| T+3:51 St 1 sep | |||
| T+3:56 SES-1 | |||
| 2211 | T+4:40 Fairing | ||
| 2215:41 | T+8:41 SECO-1 | 167 x 222 x 28.7 (Cleary) | |
| 2217 | Release subsats 1-6 (Group 1, SP1) | 172 x 286 x 28.6 | |
| 2227 | Complete Group 1 release | ||
| 2245:50 | T+38:50 SES-2 | ||
| 2245:55 | T+38:55 SECO-2 | 221 x 338 x 28.6 ? | |
| 1988 Feb 9 | 0041 | Release 5 Group 2 subsats, SP2 | |
| 0220? | Solid motor subsat released | ||
| 0258 | Canister cluster ejected | ||
| 0545 | Observe Strypi 11 launch | ||
| 0640 | Eject SPX experiment | ||
| 1022? | SES-3 Delta restart to circularize, rev 8 over Guam | ||
| 1023? | SECO-3 | 315 x 315 x 28.6? | |
| 1050? | SES-4 depletion | ||
| 1052? | SECO-4 | 290? x 318 x 30.8? | |
| Gravity gradient mode | |||
| Transmit recorded data | |||
| 1988 Feb 11 | 290 x 318 x 30.75 | ||
| 1988 Feb 19 | end of ops | ||
| 1988 Feb 28 | 278 x 299 x 30.74 | ||
| 201 x 302 x 30.7 (UN) | |||
| 1988 Apr 2 | Delta 181 reentered over Atlantic | ||
