1 Global Tropospheric Winds Sounder (GTWS) Reference Designs Ken Miller, Mitretek Systems January 24, Jan-02

2 Agenda GTWS Mission Objective Purpose Draft Wind Data Product Requirements Rapid Design Reference Instruments Reference Missions Direct Mission Conclusions Acknowledgments

3 Purpose Mission Objective is to acquire global wind velocity profiles per NASA/NOAA requirements Purpose of Briefing is to discuss Government Reference Designs for Direct and Coherent Instruments Direct Mission Coherent Mission design scheduled Feb 2002

4 Purpose of Reference Designs To establish instrument and mission architectures for reference purposes Identify tall poles (technology readiness and risk) Provide information to support a basis for government cost estimate Provide sanity check information for assessing future concepts It is not assumed that future implementations will physically match study results

5 Draft Wind Data Product Requirements Threshold and Desired requirements prepared by the GTWS Science Definition Team (SDT) Reconciled between NASA and NOAA users Threshold requirements were minimum for useful impact on models Posted for comment Oct 16, Document See Yoe/Atlas presentation

6 Rapid Design Environments at NASA GSFC ISAL Instrument Synthesis and Analysis Laboratory Rapid instrument design and concepts for remote sensing 2 week GTWS studies IMDC Integrated Mission Development Center Rapid mission engineering analyses and services Concepts, trades, technology and risk assessment 1 week GTWS studies

7 Rapid Design Areas ISALIMDC Systems Electro-mechanical Mechanical/Structural Thermal Optical Laser Electrical Integration & Test Detectors Costing Systems Mission Design Attitude Control System Propulsion Mechanical Thermal Power Command & DH Communications Flight Dynamics Flight Software Reliability Integration and Test Spacecraft bus Launch Vehicle Ground Systems Data Processing Mission Operations End of Life Disposal Costing

8 Reference Instruments Direct and Coherent lidars Meet threshold data requirements, including 0 to 20 km altitude Target Sample Volume (TSV) Maximum volume for averaging laser shots 2 perspectives per TSV Reference atmosphere including cloud coverage and shear 2 year mission life Exceptions Single laser designs may not meet lifetime requirement Single satellite did not meet temporal resolution requirement

9 Reference Instruments (cont’d) Do not provide Implementation recommendations or preferences Exhaustive technology trades Basis to compare direct and coherent approaches General limitations Based on first-cut point designs, not optimized Numerous assumptions need verification Low TRL components May not meet all requirements Requirements refined during design period Some details are competition sensitive

10 Reference Instruments- Design GTWS Team guidance on point designs Direct– Bruce Gentry (NASA GSFC), Sept 2001 Coherent– Michael Kavaya (NASA LaRC), Dec 2001 Parameters 400 km circular orbit, 97 o inclination, sun synchronous, dawn/dusk 100% duty cycle Nadir angle 45 o Scan discrete azimuth angles Point (~ 1 s) and Stare (~ 5 s) 4 cross-track soundings, 4 positions fore, 4 aft

11 Measurement Concept 7.7 km/s 400 km 585 km 414 km 290 km 45° 7.2 km/s Horizontal TSV Vertical resolution range gates 45 o nadir angle Scan through 8 azimuth angles Fore and aft perspectives in TSV Move scan position ~ 1 sec No. shots averaged ~ 5 sec * prf Aft perspective

12 Reference Instruments - Concepts Telescope with Sunshade Radiator (Solar Array not shown) Rotating Deck Coherent Direct Belt Drive Solar Array (Radiator not shown) Component Housing Component Boxes

13 IMDC Direct - October 2001 Coherent - February 2002 Large, heavy spacecraft with high power requirements 400 km orbit is challenging Altitude tradeoff between lidar SNR and orbit maintenance Solar array & radiator in orbital plane to reduce drag Battery power during eclipse (max 25 min/day) Delta L, long fairing option Current technology spacecraft Conventional hydrazine propulsion Direct Mission Highlights

14 Direct Mission Highlights (concluded) TDRSS Demand Access Downlink Controlled disposal at end-of-life COTS-based Mission Operations Center, 8x5 operations Data System Internal computer 70 Gbits storage for 3 days

15 Direct Mission Launch Configuration

16 Direct Mission - Deployed Configuration Concept TDRS Antenna SC Bus Solar Array Instrument Radiator Belt Drive Rotating Mechanism

17 Direct Mission Technology Readiness Level (TRL) Low instrument TRL: development, test, and demonstration are needed Spacecraft Overall TRL: 6 Definitions TRL 6: System/subsystem model or prototype demonstration in a relevant environment (ground or space) TRL 7: System prototype demonstration in a space environment TRL 8: Actual system completed and "flight qualified" through flight test demonstration (ground or space)

18 Conclusions Mass, size, and power are very large Need to increase instrument TRL Assumed lasers are well beyond current on-orbit laser power, efficiency, and lifetime Desirable laser improvements Increase optical output to reduce telescope size and mass Increase efficiency to reduce power and heat Increase life expectancy Increase DWL experience across range of atmospheric conditions Reduce risk: Scanner Momentum compensation Lag angle compensation Other areas

19 Conclusions (cont’d) Still a lot to learn and assess - including Fundamental differences between data products from direct and coherent lidars Global cloud and aerosol distributions Data product impacts from Clouds Aerosol distribution Wind shear Solar backscatter Spacecraft pointing and jitter

20 NASA Farzin Amzajerdian, Coherent Lidar Engineer, Robert Atlas, Science Definition Team Lead, James Barnes, GTWS Program Executive, Jennifer Bracken, ISAL Team Lead, Dave Emmitt, Senior Scientist, Bruce Gentry, Direct Lidar Principal Investigator, Gabe Karpati, IMDC Systems Engineer, Michael Kavaya, Coherent Lidar Principal Investigator, John Martin, IMDC Team Lead, Ken Miller, Systems Engineer, Mike Roberto, ISAL Systems Engineer, GTWS Team IMDC Teams ISAL Team NOAA John Pereira, Program Manager, James Yoe, Science Definition Team Lead, Acknowledgments