From: Jim Ray Subject: [IGSMAIL-2235] AMC2 RINEX procedures and observables Date: Wed, 14 Apr 1999 5:47:17 PDT ****************************************************************************** IGS Electronic Mail Wed Apr 14 5:47:17 PDT 1999 Message Number 2235 ****************************************************************************** Author: Jim Ray Subject: AMC2 RINEX procedures and observables On 08 March 1999, the AMC2 receiver at Schriever Air Force Base, Colorado Springs, CO, USA was changed from an AOA ROGUE SNR-12 (s/n T245) to a retrofitted AOA SNR-12 ACT (s/n 247-U), which is functionally equivalent to an AOA BENCHMARK ACT receiver -- see IGS Mail #2198 (10 March 1999). Beginning 16 March 1999, the data download procedures for AMC2 were changed to use TurboBinary offload files with RINEX translation done by "teqc -aoa tbY". As described by Herb Dragert in IGS Mail #2234 (12 April 1999), the AMC2 (AOA SNR-12 ACT) observables are now: C1 = C/A code at L1 freq. L1(C1) = C/A-based phase at L1 freq. P1 = Y1-codeless pseudorange at L1 freq. P2 = Y2-codeless pseudorange at L2 freq. L2(P2) = Y2-codeless-based phase at L2 freq. These differ significantly from the TurboRogue-style cross-correlation observables: C1 = C/A code at L1 freq. L1(C1) = C/A-based phase at L1 freq. P2' = codeless pseudorange at L2 freq. L2' = cross-correlated phase at L2 freq. because the P2' pseudorange-type observable and the L2' phase are actually formed by a process which tracks the cross-correlated (P2-P1) pseudorange and the (L2-L1) phase differences: P2' = C1 + (P2-P1) L2' = L1(C1) + (L2(P2)-L1(P1)) Users of AMC2 data should be aware that the new pseudorange observable pair (P1, P2) differs from the usual TurboRogue-style pseudorange pair (C1, P2') by (C1-P1) biases which are not zero-mean and can reach up to +/- 2 ns. Because the biases are satellite-dependent and receiver- dependent, they are not removed by double differencing. There is no significance for data analysts who process only the carrier phase observables. NOTE: An IGS-wide approach to handling a mix of TurboRogue-style and non-TurboRogue data will be considered at the IGS Analysis Center Workshop at SIO in June. ========================================================================= Jim Ray e-mail: jimr@maia.usno.navy.mil U.S. Naval Observatory, EO Dept. phone : 202-762-1444 3450 Massachusetts Avenue, NW fax : 202-762-1563 Washington, DC 20392-5420 ========================================================================= [Mailed From: Jim Ray (USNO 202-762-1444) ]