GPS Radio Occultation Receiver For CLARREO FY 2009 Tasks

1. GPS Radio Occultation Receiver For CLARREOFY 2009 Tasks Anthony J. Mannucci Jet Propulsion Laboratory, California Institute Of Technology

2. TriG Overview • A new GPS receiver design is needed for Decadal Survey missions, including CLARREO • Track modernized GPS and other systems (Galileo) • Track all-in-view • Improved precision and accuracy via higher antenna gain • The TriG design meets stringent climate requirements for CLARREO • Meets requirements for NOAA GPS-RO mission • Also meets the most stringent mission navigation requirements from DESDynI and ICESAT-2 • Continues climate time series started with COSMIC constellation of GPS receivers TriG

3. GPS Study Goals • Define Level 1 requirements for GPS receiver on CLARREO • Traceable to science objectives • Define implementation options • COTS? TriG? Other? • Trades: new signals, all in view, antenna, etc. • Constellation descope implications • What constellation is required for RO science? • Project-specific cost estimate and implementation timeline • Integration and test – scope and cost estimate for CLARREO • Antenna deployment environment • Nominal schedule for delivery, test, operations • Operations and data analysis plan

4. Determining Level 1 Requirements • Relevant science objectives • Poleward motion of baroclinic zones (Leroy document Nov ‘08) • Other objectives (temperature trends, refractivity trends, what altitude range?) • Level 1: • Refractivity accuracy and precision on a per-profile basis • Altitude range • Number of profiles/day in a given altitude range from the receiver • Method for estimating accuracy and precision

5. Flowdown From Level 1 • Instrument and processing system requirements • Phase and range precision and accuracy vs. boresight angle • Antenna gain and phase error versus boresight angle • On-board processing requirements (# occs/day) • Occultation scheduling • Tracking algorithms • Processing system requirements: orbit determination accuracy, ionospheric calibration, etc.

6. Trades • Key instrument trades: • Which signals? All-in-view? • Antenna gain requirements: precision and accuracy • Radiation tolerance/hardness • Parts reliability • Software class and methodology • Constellation trades – sampling error • CLARREO may meet certain science objectives with one satellite (e.g. annual climatology) • Leveraging NOAA constellation • Recommendation: CLARREO keep the GPS receiver and develops design to stringent climate specifications • Multipath environment, data processing strategy, testing and mission assurance methodology

7. Recent Activities • Implementation plan for TriG receiver • Detailed cost and schedule ready in ~3 weeks • Descope options • Partnership with Broad Reach Engineering • April workshop • Draft Level 1 requirements at a top level (broad view of objectives) • Systems engineering discussion • NOAA participation (other constellations)

8. Plans • Goals for May 2009 • Define a baseline instrument, traceable to science objectives • Define baseline science data system • Baseline accommodation requirements (antenna placement) • Baseline integration and test strategy • Cost estimate, with uncertainties • Goals following May 2009 • Constellation strategy and trades – which objectives are met with which constellation/sampling approach • Finalize GPS strategy – clearly justify GPS decision and possible coordination with NOAA constellation • Mission assurance approach and software class • Additional details on GPS receiver design and processing system • Coordination plan with Geodetic Observing System