GPS Orbits

Jim Rohde, Bob Dulaney, Bill Kass, Steve Hilla

National Geodetic Survey 2005 ConvocationOctober 24-28, 2005Silver Spring, MarylandHoliday Inn8777 Georgia Avenue

Improvements to Orbit Processing in 2004/2005

• Stars Procedure – Added redundant baselines by processing sub-networks and combining their normal equations

• Integer phase ambiguity fixing

• Moved production from HP to SUN x86 platform

• Orbit adjustment done more rigorously (ADJEPH)

• Fixed pole tide sign error

• Improved sub-daily EOP model

• Absolute Antenna Phase Center Offsets and PCVs

• Monuments as Reference Points (future)

• Updated Ocean Tide Loading Model (future)

Multiyear CORS

• Motivation– To provide long-term consistent solution of all data– Results used for CORS coordinates and velocities –

realization of NSRS– Implement recent improvements in GPS Data

Processing

• Time Span – 1994 through 2005

• Reference Frame IGb00 – IGS realization of ITRF00

Multiyear CORS (cont.)

• Procedure

– Streamline processing to fit with routine operations and avoid repeated reprocessing

– Step 1: Daily Global Solution – orbits, EOPs, IGS and some CORS site positions; solutions stacked weekly for the IGS

– Step 2: Daily CORS Solution – CORS and some North American IGS site positions; solutions stacked weekly for NAREF

– Step 3: Daily Multiyear Solution – combination of all normal equations for orbits, EOPs, and all IGS and CORS site positions

Multiyear CORS (cont.)

– Step 4: Weekly Multiyear Solution – Stack 7 daily multiyear solutions and archive results

– Step 5: Full Multiyear solution – Stack all weeks together to solve for site velocities

• Schedule – Begin processing January 2006, complete in 3-6 months