COSMIC Activities at UCAR

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COSMIC Activities at UCAR
Christian Rocken, Y.-H. Kuo, D. Ector, W.S.
Schreiner University Corporation for Atmospheric
Research
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Working on .
. getting from here
to here
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COSMIC Program Office Responsibilities

• Developing the COSMIC Data Analysis and Archive
  Center Mission Data Analysis / Result
  Distribution
• Management of the payload subcontracts for GPS,
  TIP, and CERTO/TBB
• The launch contract
• Support of the development of the Taiwan Analysis
  Center for COSMIC (TACC)
• Establishment and operation of two dedicated
  high-latitude Earth stations
• Obtaining GPS fiducial data and auxiliary
  meteorological data needed for the mission
  analysis.
• Science / Science mission requirements trade
  studies

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CDAAC Status

• CDAAC prototype has been developed
• Processing data from GPS/MET / CHAMP / SAC-C
• Comparison of results with JPL and GFZ has begun
• Web based archiving and research tool is
  available
• Real-time processing under development (180 min.
  requirement)

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Tiny Ionospheric Photometer

• TIP measures nighttime FUV (135.6 nm) emission of
  neutral atomic oxygen
• TIP and GPS data can be processed together for
  improved ionsopheric profiling
• Radiative recombination Oe- ? Oh?
• Simple algorithm relates electron density to
  135.6 nm intensity measured by TIP
• Aurora TIP can determine auroral boundaries

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COSMIC Beacon Concept
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COSMIC GPS Receiver ARGO
JPL Design, ARGO is based on CHAMP BlackJack
Receiver Technology transfer JPL - Broad Reach
Engineering 4 antennas 2 occultation 2 POD
antennas Receiver Antennas Data Recorder/PC
5.6 kg Power 16W GPS 10 W Data Recorder/PC New
open loop tracking and software for rising
occultations under development at JPL
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General RGS Requirements

• Two Remote Ground Stations (RGS) North Pole,
  Alaska and Kiruna, Sweden
• Approximately 42 Satellite Contacts / Day From
  Each Tracking Station
• System Availability 95 (TBR), System
  Reliability 98
• Tracking Station Telemetry Storage Capacity 40
  Gbytes for COSMIC Data
• Provide RGS Monitoring Information to NSPO
• Provide Non-Real-Time Data Ready for FTP
  Message to CDAAC Within 2-Minutes After Data Is
  On Server (CDAAC Performs FTP-Pull)

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Launch

• Launch scheduled for late 05
• All 6 satellites launched on a single USAF
  Minotaur Rocket
• Use differential precession to reach final orbits
  within 13 months of launch
• Data collection during the orbit drifting phase
  will afford opportunity for special studies
  (dense occultation coverage initially, gravity
  research during lower orbits, .)

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Science Issues / Trade Studies

• Trade studies
• Constellation configuration
• Antenna gain/patterns and antenna mounting
• Occultation counts
• Science Issues
• Lower troposphere GPS signal tracking inversion
• GPS sampling rates (for gravity, ionosphere,
  troposphere)
• GPS errors obtaining profiles with associated
  uncertainties
• Comparing Radio Occultation with other new
  observing systems (i.e. AQUA satellite)
• TIP Beacon data analysis in combination with
  GPS
• Latency requirements for ionospheric products
• Gravity studies and constellation
• Orbit drift phase studies
• Data use and assimilation

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Sounding Coverage for 3 Different Constellations
(sun-fixed frame)
3 Orbit Planes
6 Orbit Planes, 24 deg.
6 Orbit Planes, 30 deg.
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COSMIC EQUARS Radiosondes
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Effect of Spacecraft Pointing Errors
Effect of s/c pitch
Effect of s/c roll
Effect of pointing error
Earth Limb
High-gain antenna FOV
Effect of s/c yaw
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Occultation Counts
Az(ant frame) Number of scheduled
occultations 35deg 459 (2736) 39deg 511
(3066)
Limb
Limb -2
Assumptions 28 s/c 7.5 x 50 deg FoV 10
dB 24 Hours 100 of scheduled occultations
succeed
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CHAMP Occultation Counts
Reasons for Profile Failure (1 week in 2002)
1571 occs with some leo data (225occ/day)
139 failed calibration of excess phase due
to no fiducial data amtPrf Stats for CHAMP,
2002.091-097 1432 of atmPhs files 1432
number of atmPrf files 1104 ( 77.1 percent)
OK (160occ/day) 173 ( 12.1 percent) STARTS
TOO LOW 28 ( 2.0 percent) ENDS TOO HIGH 36
( 2.5 percent) NO CONVERGENCY IN RAY 0 ( 0.0
percent) PROBLEM IN CT METHOD 8 ( 0.6
percent) Bad alt, ref, pres or temp 24 ( 1.7
percent) S4 0 ( 0.0 percent) nidelta 48
( 3.4 percent) difmaxref 14 ( 1.0 percent)
difmaxion 2 ( 0.1 percent) stdv 6 ( 0.4
percent) smean
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Tracking GPS Reference Satellites

• (a) GPS1 has to be occulting (b) GPS2 has to be
  tracked at high rate (100 Hz) GPS1 GPS2 must
  be seen from ground receiver

POD Antenna FOV ( 3 dB)
Limb antenna FoV 3 dB
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Reference Satellite Tracking
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Summary

• Work on COSMIC is progressing well and CDAAC,
  payloads, launch contract, ground stations are
  all on track
• At this point the formation of science teams for
  COSMIC is important to help answer open issues,
  set priorities and maximize science
• Radio Occultation Technique
• Radio Occultation Meteorology/Climate
• Ionosphere Space Weather
• Space Geodesy, Gravity, Orbits
• Please consider active participation in Cosmic
  Science Working Groups!

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NRL Radio Beacon Sensors in Space
CERTO on C/NOFS
SCITRIS I
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TIP Instrument Heritage
Direct heritage of the prototype the CERTO/PLUS
Payload Which Flew on STRV-1D on 17 November
2000. Also, heritage from other flight programs
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Systems Engineering

• Design Overview

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PoD Antennas

• Number 2 per satellite
• Gain 4 db peak L1 L2 for /- 60 from
  boresight
• Phase center variation for /- 90 from boresight
• Type RHCP L-band, L1/L2 patch (TBD)
• Antenna calibration needs to be done for an
  antenna that is mounted on the satellite or
  full-scale model
• Also to be used for ionospheric and reference
  satellite tracking - gain requirement to track
  reference satellites at 50-100 Hz is 3 dB

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Current Requirements
2500 GPS soundings / day (requires rising
setting occultations, assuming 28 functional
GPS satellites (as in the current June 2002
constellation), all six COSMIC satellites are
working and that some soundings may have to be
tracked in part outside of the high gain
occultation antenna FOV
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Occultation Antennas

• Number 2 per satellite (1 forward and 1 aft)
• Gain L1 10 db (L2 8 db) within /- 7 ele x /-
  40 horizontal FOV from boresight
• Phase center variation 1.9 mm/degree elevation
  change knowledge within high gain FOV dimension
  and 4.7 mm/degree azimuth change knowledge
  within high gain FOV dimension
• Gain variation knowledge needs to be better than
  TBD / degree elevation and better than TBD /
  degree azimuth change within high-gain FOV
• Type dual frequency, RHCP L-band, design
  multiple patch TBD
• Antenna calibration needs to be done for an
  antenna that is mounted on the satellite or
  full-scale model
• Boresight shall be oriented towards Earth limb

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Tracking

• Occultation tracking 2 setting 1 rising GPS (or
  two rising and 1 setting) occultations
  simultaneously
• POD tracking "all in view" up to 9
• L1, L2 phase up to 100 samples / sec
• L1 (L2) amplitude up to 100 samples / sec

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Pitch
Roll
Yaw
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Effect of s/c Pitch Error

• 2 deg. change in pitch has 10-15 effect on
  occultation count
• Random 2 deg. pitch error will average out to 1st
  order
• Probably need to lower boresight to 3 degrees
  below limb
• Effective beamwidth is 30 smaller than antenna
  azimuth beamwidth
• 2 deg. pitch error has to be 2-sigma

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• 5 deg. change in roll has insignificant impact on
  count
• Random 5 deg. roll error will average out to 1st
  order

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• 5 deg. change in yaw has insignificant impact on
  count
• Random 5 deg. pitch error will average out to 1st
  order

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Orbit Requirements
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Trade Study for Velocity Requirement
0.5 mm/sec
0.1 mm/sec
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GPS Observation Goals for COSMIC

• 2500 Profiles / day (assume 28 GPS sats. Some
  occs. may not be completely in high-gain FOV)
• Global distribution (6 orbit planes)
• 90 of the profiles (75 of tropical profiles)
  L1 is tracked into the lowest 1-km (to -150 km
  LOS)
• L2 down to about 5 km sufficient

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Phase and Range Requirements

• L1, L2 instrumental phase error points with SNR (1-sec) 100, A/S - on,
  excluding multipath)
• L1, L2 instrumental pseudorange error (10-sec points with SNR (1-sec) 100, A/S -on,
  excluding multipath)
• To be tested with zero-baseline double
  differences

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Amplitude measurement

• L1 amplitude is required
• SNR data reported in integer values of 1-second
  SNR, ranging from 1 to 5000.
• Amplitude rate of change due to the receiver
  shall be

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CDAAC Result Latency
Transfer Analysis
On-Orbit Data Collection
Average age of data when sent to users 100
minutes feasible goal (180 minutes requirement)
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Conclusions

• UCAR is working with OSC, BRE, JPL and NRL to
  ensure that COSMIC science goals can be met
• Studies are conducted
• placement of antennas
• stability requirements
• orbit constellation
• sampling rate
• sounding penetration
• Good collaboration among COSMIC partners will
  ensure COSMIC science