Global Tropospheric Winds Sounder GTWS Reference Designs

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Global Tropospheric Winds Sounder(GTWS)Reference
Designs

• Ken Miller, Mitretek Systems
• January 24, 2002

15-Jan-02
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Agenda

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

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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

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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

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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, 2001
• http//nais.msfc.nasa.gov/cgi-bin/EPS/sol.cgi?acqi
  d99220Draft Document
• See Yoe/Atlas presentation

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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

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Rapid Design Areas
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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

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Reference Instruments (contd)

• 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

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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

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Measurement Concept
7.7 km/s

• 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
45
585 km
400 km
45
Horizontal TSV
414 km
7.2 km/s
290 km
290 km
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Reference Instruments -Concepts
Solar Array (Radiator not shown)
Belt Drive
Telescope with Sunshade
Rotating Deck
Component Boxes
Direct
Radiator (Solar Array not shown)
Component Housing
Coherent
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Direct MissionHighlights

• 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

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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

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

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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

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Conclusions (contd)

• 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

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Acknowledgments
NASA Farzin Amzajerdian, Coherent Lidar Engineer,
f.amzeajerdian_at_larc.nasa.gov Robert Atlas,
Science Definition Team Lead, robert.m.atlas.1_at_gsf
c.nasa.gov James Barnes, GTWS Program Executive,
j.c.barnes_at_larc.nasa.gov Jennifer Bracken, ISAL
Team Lead, jennifer.bracken_at_gsfc.nasa.gov Dave
Emmitt, Senior Scientist, gde_at_swa.com Bruce
Gentry, Direct Lidar Principal Investigator,
bruce.m.gentry.1_at_gsfc.nasa.gov Gabe Karpati, IMDC
Systems Engineer, gkarpati_at_pop700.gsfc.nasa.gov
Michael Kavaya, Coherent Lidar Principal
Investigator, m.j.kavaya_at_larc.nasa.gov John
Martin, IMDC Team Lead, jmartin_at_pop400.gsfc.nasa.g
ov Ken Miller, Systems Engineer,
kenm_at_mitretek.org Mike Roberto, ISAL Systems
Engineer, mroberto_at_pop700.gsfc.nasa.gov GTWS
Team IMDC Teams ISAL Team NOAA John Pereira,
Program Manager, john.pereira_at_noaa.gov James Yoe,
Science Definition Team Lead, james.g.yoe_at_noaa.gov