DORIS/JASON data What is happening in the South Atlantic Anomaly region? P. Willis (IGN/JPL),B. Haines (JPL), Y. Bar-Sever (JPL), L. Young (JPL) Marne-la-Vallee IDS Analysis Workshop 1/15 Fevrier 2003 SUMMARY • Problems found with DORIS/JASON data – DORIS tracking stations weekly positioning – Master stations clock monitoring – Precise Orbit Determination (with or without DORIS/SAA data) • Physical explanation – JASON clock behavior in the SAA region – Does it explain the above mentioned problems? • Conclusions Marne-la-Vallee IDS Analysis Workshop 2/15 Fevrier 2003 Map from H. Fagard Marne-la-Vallee IDS Analysis Workshop 3/15 Fevrier 2003 Station outside SAA DORIS/JASON weekly station positoning Station inside SAA (latitude, longitude, altitude) cycle 1 to 33 =January 15 - December 8, 2002 150 100 50 0 -50 -100 -150 2002 2002.2 2002.4 2002.6 2002.8 2003 Year Marne-la-Vallee IDS Analysis Workshop 4/15 Fevrier 2003 YARB vertical YARB longitude YARB latitude DORIS/JASON weekly point positioning cycle 1 to 33 (Jan 15 - October 8, 2002) station Yaragadee (YARB) 150 100 50 0 -50 -100 -150 2002 2002.2 2002.4 2002.6 2002.8 2003 Year Marne-la-Vallee IDS Analysis Workshop 5/15 Fevrier 2003 KRUB vertical KRUB longitude DORIS/JASON weekly point positioning KRUB latitude cycle 1 to 33 (Jan 15 - October 8, 2002) station Kourou (KRUB/KRVB) 150 100 50 0 -50 -100 -150 2002 2002.2 2002.4 2002.6 2002.8 2003 Year Marne-la-Vallee IDS Analysis Workshop 6/15 Fevrier 2003 CACB vertical CACB longitude CACB latitude DORIS/JASON weekly point positioning cycle 1 to 33 (Jan 15 - October 8, 2002) station Cachoeira (CACB) 150 100 50 0 -50 -100 -150 2002 2002.2 2002.4 2002.6 2002.8 2003 Year Marne-la-Vallee IDS Analysis Workshop 7/15 Fevrier 2003 PDMB vertical (TOPEX data) PDMB vertical (JASON data) 1-satellite station weekly positioning station Ponta Delgada (PDMB) 40 20 0 -20 Difference with ITRF-2000 (in cm) -40 2002 2002.2 2002.4 2002.6 2002.8 2003 2003.2 Year Marne-la-Vallee IDS Analysis Workshop 8/15 Fevrier 2003 Marne-la-Vallee IDS Analysis Workshop 9/15 Fevrier 2003 Marne-la-Vallee IDS Analysis Workshop 10/15 Fevrier 2003 TOPEX DORIS RMS JASON DORIS RMS (SAA stations included) JASON DORIS RMS (without SAA data) 5 10-7 4.5 10-7 4 10-7 3.5 10-7 0 50 100 150 200 250 Day of Year (in 2002) Marne-la-Vallee IDS Analysis Workshop 11/15 Fevrier 2003 Act u la JASON cl ock ehavb i o (sr atellite clock equencyfr ) SAA SAA SAA JASON sa tel lit ecl o c ink the DORIS data (af ter rem o avl of a long-ter m polynomal byi CNES in their prep r ceo ssi n g= ) SAA SAA SAA Marne-la-Vallee IDS Analysis Workshop 12/15 Fevrier 2003 Stati on at the bounda r y of the SAA re g ino North N orth DESCE NDINGPA SS AT K OROU U ASCEN DINGP ASS AT KOUROU Marne-la-Vallee IDS Analysis Workshop 13/15 Fevrier 2003 Stati on in the middle of the SAA r e gio n North N orth DESCE NDINGPA SS AT CAC H OIERA ASCEN DINGP ASS AT CACHOIER A Marne-la-Vallee IDS Analysis Workshop 14/15 Fevrier 2003 CONCLUSIONS • Problems found with JASON/DORIS data can be explained by radiation effects on on-board clock in the SAA region • Problems presently are getting worse almost linearly with time (January - December 2002) • Future work – New preprocessing ? – New estimation strategy (with or without the SAA data)? Marne-la-Vallee IDS Analysis Workshop 15/15 Fevrier 2003.