SUBJ: GPS STATUS 23 MAY 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 PLANE : SLOT B2, E1, D2, F2, F3, A4, B3 CLOCK : CS, CS, RB, 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 098-90136 161631Z MAY 90 PRN9 ADV UNUSABLE 136/1451-136/1535 099-90136 162101Z MAY 90 PRN12 FCST CHANGE REPHASE TO 141/2056 PRN20 FCST STATIONKEEPING ON 156/0025 100-90136 162107Z MAY 90 PRN2 FCST UNUSABLE 144/1200-145/0230 101-90137 171348Z MAY 90 PRN9 ADV UNUSABLE 137/1040-137/1100 102-90137 171909Z MAY 90 PRN6 ADV UNUSABLE 137/1304-137/1350 103-90142 220500Z MAY 90 PRN3 ADV UNUSABLE 142/0820-142/0835 104-90143 231531Z MAY 90 PRN2 FCST UNUSABLE 145/1200-146/0230 3. REMARKS: A. 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. 4. SATELLITE REPOSITIONING: NOTE ADDITION OF PRN20 TO SCHEDULE PRN INITIATE TERMINATE#1 TERMINATE#2 UNUSABLE (DAY/UTC) 11 15 MAR 90 31 OCT 90 74/0335-75/0225 ACTUAL 3 20 MAR 90 17 OCT 90 79/0700-79/1220 ACTUAL 13 29 MAR 90 3 OCT 90 88/0142-88/1105 ACTUAL 18 7 APR 90 24 NOV 90 8 DEC 90 97/0318-97/1902 ACTUAL 19 11 APR 90 101/0421-101/0634 RESCHD 19 12 APR 90 31 DEC 90 102/0440-102/1411 ACTUAL 9 19 APR 90 19 APR 90 109/2126-110/2126 RESCHD 9 21 APR 90 21 APR 90 111/1035-111/1440 ACTUAL 16 26 APR 90 20 SEP 90 116/0736-116/1509 ACTUAL 2 3 MAY 90 1 DEC 90 123/1906-124/0646 ACTUAL 14 14 MAY 90 10 NOV 90 134/0116-134/1013 ACTUAL 12 21 MAY 90 22 MAY 90 141/2230-142/0820 ACTUAL 20 5 JUN 90 6 JUN 90 156/0025-157/0025 FORECAST 5. POINT OF CONTACT: MAJ FAUVER AT (719)550-6379.