1 Global Tropospheric Winds Sounder (GTWS) Reference Designs Ken Miller, Mitretek Systems January 24, 2002 15-Jan-02
Jan 01, 2016
1
Global Tropospheric Winds Sounder(GTWS)
Reference Designs
Ken Miller, Mitretek SystemsJanuary 24, 2002
15-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 ProductRequirements
• 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, 2001http://nais.msfc.nasa.gov/cgi-bin/EPS/sol.cgi?acqid=99220#Draft
Document
• See Yoe/Atlas presentation
6
Rapid Design Environmentsat 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
ISAL IMDC
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, 97o 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
290 km
45°
45°
7.2 km/s
HorizontalTSV
• 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 2920-10L, long fairing option • Current technology spacecraft• Conventional hydrazine propulsion
Direct MissionHighlights
14
Direct MissionHighlights (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 MissionLaunch Configuration
16
Direct Mission - Deployed Configuration Concept
TDRS
Antenna
SC Bus
Solar
Array
Instrument
Radiator
Belt Drive
Rotating
Mechanism
17
Direct MissionTechnology 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
NASAFarzin Amzajerdian, Coherent Lidar Engineer, [email protected] Atlas, Science Definition Team Lead, [email protected] Barnes, GTWS Program Executive, [email protected] Bracken, ISAL Team Lead, [email protected] Emmitt, Senior Scientist, [email protected] Gentry, Direct Lidar Principal Investigator, [email protected] Karpati, IMDC Systems Engineer, [email protected] Michael Kavaya, Coherent Lidar Principal Investigator, [email protected] Martin, IMDC Team Lead, [email protected] Miller, Systems Engineer, [email protected] Roberto, ISAL Systems Engineer, [email protected] TeamIMDC TeamsISAL Team
NOAAJohn Pereira, Program Manager, [email protected] Yoe, Science Definition Team Lead, [email protected]
Acknowledgments