GPS OPERATIONAL ADVISORY 90253.OA1
SUBJ: GPS STATUS 10 SEP 90
1. SATELLITES, PLANES AND CLOCKS (CS=CESIUM RB=RUBIDIUM):
SLOTS MAY NOT BE FINAL UNTIL AFTER 21-SATELLITE REPHASING
A. BLOCK I : PRNS  3,  6,  9, 11, 12, 13
   PLANE   : SLOT D1, A3, A2, C2, A1, C1
   CLOCK   :      RB, RB, RB, CS, CS, CS
B. BLOCK II: PRNS  2, 14, 16, 17, 18, 19, 20, 21
   PLANE   : SLOT B2, E1, E3, D2, F3, A4, B3, E2
   CLOCK   :      CS, CS, RB, CS, CS, CS, CS, CS
2. CURRENT ADVISORIES (ADV) AND FORECASTS (FCST):
INFORMATION IS REPEATED FOR SEVEN DAYS AFTER EVENT CONCLUDES
NANU      MSG DATE/TIME   PRN    TYPE  SUMMARY
172-90234 221704Z AUG 90  RPOSN  FCST  REPOSITIONING SCHEDULE
183-90247 040500Z SEP 90  PRN13  ADV   UNUSABLE 247/0313-247/0340
184-90247 041955Z SEP 90  PRN11  ADV   UNUSABLE 247/1517-247/1630
185-90249 050800Z SEP 90  PRN6   ADV   UNUSABLE 248/0400-248/0413
186-90248 051449Z SEP 90  PRN15  FCST  REPOSITN 249/0256-250/0256
187-90252 091345Z SEP 90  PRN13  ADV   UNUSABLE 252/0620-252/0650
188-90252 091350Z SEP 90  PRN6   ADV   UNUSABLE 252/1300-252/1315
3. REMARKS:
A. PRN21 IS USABLE AS OF DAY 234 (22 AUG 90) AT APPROXIMATELY
1500 UTC. ALTHOUGH THE SATELLITE IS USABLE FOR NAVIGATION AND
TIMING, IT HAS NOT BEEN DECLARED OPERATIONAL AND IS UNDERGOING
TESTING THAT MAY RESULT IN PRN21 BEING SET UNUSABLE WITHOUT
ADVANCE NOTIFICATION.
B. IMPLEMENTATION OF STANDARD POSITIONING SERVICE:
THE CURRENT GPS CONSTELLATION BEGAN BROADCASTING NAVIGATION
MESSAGES AT ACCURACY LEVELS CONSISTENT WITH STANDARD POSITIONING
SERVICE ON 25 MAR 90. GPS IS NOT EXPECTED TO BE DECLARED FULLY
OPERATIONAL UNTIL 1993. ANY GPS USERS ARE OPERATING AT THEIR OWN
RISK.
C. THE SATELLITES WHICH BEGAN REPOSITIONING EARLIER THIS YEAR WILL
CONTINUE GRADUAL CHANGES TO THEIR ORBITAL POSITIONS UNTIL
REPOSITIONING TERMINATE DATES AS SHOWN BELOW:
PRN  TERMINATE  TENTATIVE OUTAGE WINDOWS (UTC)
16    6 SEP 90  FINAL MANEUVER 249/02:56-250/02:56
13   18 SEP 90  FINAL MANEUVER 261/15:32-262/15:32
 3   15 OCT 90  FINAL MANEUVER 288/19:17-289/19:17
11   25 OCT 90  FINAL MANEUVER 298/17:08-299/17:08
14    2 NOV 90  FINAL MANEUVER 306/01:08-307/01:08
18   13 NOV 90  SLOW DOWN      317/02:14-318/02:14
 2   20 NOV 90  FINAL MANEUVER 324/09:26-325/09:26
18   10 DEC 90  FINAL MANEUVER 344/00:29-345/00:29
19   19 DEC 90  SLOW DOWN      353/19:04-354/19:04
19   10 JAN 90  FINAL MANEUVER 010/00:14-011/00:14
4. POINT OF CONTACT: MAJ FAUVER AT (719)550-6379.