Transcript COSMIC: A Microsat Constellation K. F. Dymond, S. A. Budzien, P.

COSMIC: A Microsat Constellation
K. F. Dymond, S. A. Budzien, P. A. Bernhardt
(Naval Research Laboratory)
and
C. Rocken, S. Syndergaard
(University Corporation for Atmospheric Research
Additional Contributors
• AFRL
–
–
–
–
Todd Pederson
Chin Lin
Keith Groves
Santi Basu
• NRL
– Carl Siefring
– Clayton Coker
– Damien Chua
• UCAR
– Doug Hunt
• Broad Reach
Engineering
– Chris McCormick
COSMIC/FORMOSAT-3
• Constellation Observing System
for Meteorology, Ionosphere, and
Climate
• US-Taiwan Collaboration
• Launched April 14, 2006 (PST)
• Six microsatellites
• Scientific Payload
Orbital Sciences Corp
.
– GOX (GPS Occultation eXperiment)
– TIP (Tiny Ionospheric Photometer)
– TBB (Tri-Band Beacon)
COSMIC Satellites
Tiny Ionospheric
Photometer
Tri-band Beacon
GPS Occultation
Experiment
6 Micro Satellites - USAF Minotaur
Rocket Integration
COSMIC - Final Deployment
•6 Planes
•71 Degrees
inclination
•800 Km
•2500 Soundings
per day
•Latency 50-140
minutes from
observation to
NOAA
Instruments
• GPS Occultation Experiment (GOX)
– Very high precision GPS occultation receiver
– Limb (slant) TEC measurements, refractivity
• Tiny Ionospheric Photometer (TIP)
– Very high sensitivity UV photometer
– Nighttime 135.6 nm radiance
• Tri-Band Beacon (TBB, CERTO)
– Very high accuracy coherent radio beacon
– Near-vertical relative TEC measurements
– Satellite-to-satellite TEC measurements
GOX – GPS Occultation
Tangent point
vGPS
LEO
vleo
The velocity of GPS relative to
LEO must be estimated to ~0.2
mm/sec (20 ppb) to determine
precise temperature profiles
The LEO tracks the GPS phase
while the signal is occulted to
determine the Doppler
COSMIC GPS Occultation Soundings in 1 Day
COSMIC
Radiosondes
Sec 3, Page 10
How does GPS occultation work?
Atmospheric refractive index n  c / v where c is the speed of light
in a vacuum and v is the speed of light in the atmosphere
Refractivity
N  106 (n  1)
P
5 Pw
6 ne
N  77.6  3.73 10 2  40.3  10 2
T
T
f
(1)
(2)
(3)
• Hydrostatic dry (1) and wet (2) terms dominate below 70 km
• Wet term (2) becomes important in the troposphere and can
constitute up to 30% of refractivity at the surface in the tropics
• In the presence of water vapor, external information information is
needed to obtain temperature and water vapor
• Liquid water and aerosols are generally ignored
• Ionospheric term (3) dominates above 70 km
Using COSMIC for Hurricane Ernesto Prediction
With COSMIC
Without
GOESCOSMIC
Image
GOES Image from Tim Schmitt, SSEC
Comparisons with ISR data
[Lei et al., submitted to JGR 2007]
Scintillation Sensing with GOX/COSMIC
No scintillation
S4=0.005
Scintillation
S4=0.113
Source of the scintillation
can be located using
back-propagation
GPS/MET SNR data
GOX Performance
• GOX produces ~2500 high quality occultations
over the globe each day
– Temperature/refractivity
– Ionospheric TEC
– Improvements to tropospheric weather forecasting have
been demonstrated
• Ionospheric validation campaigns have been
successful
– Inclusion of TIP data should help improve
reconstructions in areas of high gradients
– Can also use TBB data with GOX for improved regional
electron density specification
Tiny Ionospheric Photometer (TIP)
• Nighttime: Radiative recombination
– O++e-  O+h
– O+ and e- densities equal in the Fregion
– Intensity of 135.6 nm emission is
proportional to electron density
squared
– Simple algorithm relates electron
density to 135.6 nm intensity
measured by TIP
•
How are TIP measurements used?
– Ionospheric gradients
– Ionosphere/Thermosphere
morphology
– Simple VEC estimates
• (vertical electron content)
– GOX-TIP, TBB-TIP joint retrievals
– GAIM (Assimilative modeling)
TIP Observations of Variability of Tropical Arcs on14
Sept. 14, 2006
Global pattern is similar to observations by IMAGE FUV at
equinox – attributed to atmospheric tides by Immel et al.
2006
Comparison of TIP and all-sky imager
17 Sept. 2006
~1.5e12/m3
1103
100 km
~7e11/m3
1-2% measurement noise
enhanced
N. crest
S. crest
mid lat
1104
1105
1106
1107
TIP Pass Directly Over SCINDA Line-of-sight
18 Sept. 2006
244-MHz Scintillation
108 counts (2σ noise)
1e5/cm3
~1e6/cm3
1000
1200
1400
source Todd Pedersen AFRL
100 km
~6e5/cm3
SCINDA LOS
magnetic
equator
mid lat
Comparison of TIP and Radio Occultation
14 Sep 2006 FM1 FM3 FM4 FM6
2100 LT
Rayleighs
Rayleighs
TIP 135.6-nm
Radiance
RO-derived 135.6-nm
Radiance
Magnetic Latitude
TIP/GPS Tomography Study 15 Sept 2006
• Only data in orbits 1 & 3 were used in this study
• The TEC data in orbit 2 showed a data drop-out just above the F2
layer peak & so the inversion could not be adequately constrained
by the data
Indicates location of occultation
Kwajalein
Orbit 3
Orbit 1
Inversion Results from 15 Sept 2006 – Orbit 3
• Left panel shows the observed TEC (*) and the fit (-)
• Panel on right shows TIP radiances (-) and the fit (-)
• TEC and radiance variations and magnitudes are
consistent with a low- and mid-latitude ionosphere
typical of solar minimum conditions
Inversion Results from 15 Sept 2006 – Orbit 3
• 2-D ionosphere is shown on left (units are electronscm-3)
• Panel on right shows nmF2 variation
• Density variations and magnitudes are consistent with
a low- and mid-latitude ionosphere typical of solar
minimum conditions
Tomographic results have been
used to validate the TIP calibration
to be ~700 ct/s/R for FM6!
TIP Summary
• 6 COSMIC Spacecraft with TIP Sensors
Operating
– TIP Sensors Performing as Expected
– Issues to watch
• Terminator glint avoidance
• Calibration stability
• “Red” sensitivity characterization
• TIP’s High Sensitivity and High Spatial
Resolution Permits
– Ionospheric Tomography With GOX
– Studies of Appelton Anomalies and Inference of
Ionospheric Drivers
– Studies of Equatorial Spread-F
TBB/CERTO – Ionospheric TEC and
Scintillation Data
– Ionospheric Data Needs - Alert Users to Impending Problems
• UHF SATCOM and GPS disruptions
• UHF/L-Band Synthetic Aperture Radar (SAR) degradation
• Reduced Accuracy of Operational Over-the-Horizon (OTH) Radars
– Currently Available Ionospheric Data Sources
• Dual Frequency GPS Receivers (TEC) – Ground and Space
• DORIS Geodetic Receivers on SPOT2-4, Topex/Poseiden, Jason-1,
Envisat (TEC)
• Air Force RADCAL Receivers of RADCAL, GFO, DMSP/F15 (TEC)
• NWRA/U. Alaska Tomography Array with Scintillations (TEC/Scintillations)
– New Ionospheric Data Sources
• CERTO Beacons on DMSP/F15, COSMIC (6), CASSIOPE/ePOP, C/NOFS,
EQUARS
• CITRIS Receiver on STPSAT1
JOINT CERTO/TBB, GPS-GOX, TIP
OPERATIONS ON COSMIC
From GPS
Satellite
TIP EUV
Field of View
Satellite to Ground
Relative TEC
Ground Receivers
CERTO/TBB Tomography
•Ionospheric Reconstruction
– Synthetic Electron Density Data
from SAMI3 Model
– Derived TEC for Ground Receivers
– Reconstructed Electron Densities
Ionosphere Model Densities
TEC (1016 cm-2)
Electron Density
Reconstruction
Input TEC Data
Latitude
RADCAL Observations of TBB/CERTO
• Air Force RADCAL Receiver Network
–
–
–
–
20 Magnavox MX 1502 DS Receiver Sites
Records TEC from 150 and 400 MHz for RADCAL and GFO
Support for TBB/CERTO is Under Request to Air Force
NRL Writing Data Conversion Software for RADCAL Format
Thule
Poker Flat
Hill AFB
Pillar Pt
VAFB Edwards
White Sands
Pt Mugu
Wallops Is
Patrick AFB
Kaena Pt
Antigua
Kwaj
Ascension
COSMIC FM1, FM5, FM6 TEC at Patrick AFB, FL
21 December 2006, 02:51 to 07:19 UT (21:51 to 02:19 LT)
Relative Slant TEC 1016 m
2
COSMIC11 Patrick AFB
12 213 2006 05:07:49
2
4
0
North
West
10 20 30 40 50 60 70 80 90
Zenith Angle (Deg)
South
East
NRL Radio Beacon Sensors
CERTO on RADCAL
DMSP/F15 1998
SEEK2 Rockets
August 2002
CERTO on
PICOSat
(2001-2005)
Past
CERTO/TBB
on COSMIC
(2006)
Note: Each Beacon Satellite
has Independent Ionospheric
Sensors
CITRIS on
STPSAT1
(2007)
Future
CERTO on
ARGOS
(19992001)
CASSIOPE
(2008)
CERTO on
C/NOFS
(2008)
CERTO
EQUARS
(2009)
Scintillation and Ionospheric Tomography
Radio Instrument in Space (CITRIS):
Space Based Monitor of DORIS Ground Beacons or
Tandem Operations of COSMIC & STPSAT1
CERTO on
COSMIC
CITRIS on
STPSAT1
RF Link
COSMIC/CITRIS Operations
– Simultaneous VHF/UHF/L-Band
– About 25 Satellite to Satellite Links
Per Day
– Average 2.8 Hours of Data Collection
Per Day
– TEC Inputs to Space Weather Models
– Global Scintillation Monitor
DORIS
Station in
Australia
28 April 2007 CITRIS-DORIS TEC Data
30 April 2007 CITRIS-CERTO TEC Data
CERTO/TBB Summary
Satellite to Ground Systems Using Beacons and Receivers
Provide Global TEC Data with Some Scintillation Indications
(GPS, RADCAL, DORIS, CERTO)
• CITRIS is an Orbiting VHF/UHF/L-Band Receiver
– High Rate (200/s) Samples of Phase and Amplitude
– Ground and Low Earth Orbit (LEO) Beacon Sources
• Scintillation Now-Casting Using CITRIS Data from DORIS
Beacons
– Scintillation and Tomography Receiver in Space (CITRIS)
– Ground DORIS Beacons at 401.25 and 2036.25 MHz
– Validation with CERTO and GPS Beacons
• CITRIS Flown on Air Forced Space Test Program STPSAT1
– February 2007 Launch
– 35° Inclination at 560 km Altitude
Summary
• COSMIC generates large amount of high quality space
weather data
• Data available for real-time (significant amount of data with
less than 60 min latency) and for post-processing
– Freely available from NCAR website
• Data are used for model comparison /improvement
• Global scintillation data will be available within months
• High temporal and spatial resolution
– ~1 second nominal GOX sampling
– TIP ~30 km along-track resolution
• Can go to higher sampling rate for ~15 km resolution
• Nominal sensitivity is 0.002 Rayleighs/count
– TBB sampling can be high using ground-based receivers
• CITRIS sampling at 200 Hz
STPSAT1 Conjunction with
the COSMIC2 Satellite
RADCAL/GFO Beacon Satellites
• 20 RADCAL Ground
Stations
– Archived Data 1993
to Present
– 5 Second Samples
– Maintained by AF
Western Test Range
Vandenberg
RADCAL (1993 to Present)
• 3 RADCAL/GFO
Satellites
• Radio Altimetry and
Ephemeris
Satellites
– 150/400 MHz Radio
Beacon
– Ionospheric TEC
Correction Data
GFO (1998 to Present)
RADCAL on DMSP/F15
(Aug 2006 to Present)
CERTO Beacon Orbits
Scintillation and Ionospheric Tomography
Radio Instrument in Space (CITRIS):
Tandem Operations of COSMIC and STPSAT1
CERTO on COSMIC
CITRIS on
STPSAT1
RF Link
COSMIC/CITRIS Operations
–
–
–
–
–
Simultaneous VHF/UHF/L-Band
About 25 Links Per Day
Average 2.8 Hours of Data Collection Per Day
TEC Inputs to Space Weather Models
Global Scintillation Monitor
TIP measurements
• TIP measures nighttime FUV emission of
neutral atomic oxygen
• Radiative recombination: O++e-  O+h
– 135.6 nm produced by radiative recombination
of O+ ions and electrons
– O+ and e- densities equal in the F-region
– 135.6 emission intensity proportional to
electron density squared
– Simple algorithm relates electron density to
135.6 nm intensity measured by TIP
• Aurora: O+e-  O +e- +h
– 135.6 nm produced in aurora through electron
impact excitation
– TIP can determine auroral boundaries
TIP 135.6-nm passes 14 Sep 2006
7-11 UT (2100 LT)
From presentation by Santimay Basu, AFRL
TIP observations over large area on 14 Sep 2006
FM6 pass 1042UT
FM6 pass 0907UT
FM6 pass 0730UT
FM3 pass 1050UT
FM3 pass 0914UT
FM3 pass 0738UT
FM4-PINH pass 1050UT
FM4-PINH pass 0914UT
FM4-PINH pass 0738UT
FM1 pass 1140UT
FM1 pass 1005UT
FM1 pass 0828UT
First Collocated Ionospheric Profiles
From presentation by Stig Syndergaard,
UCAR/COSMIC
COSMIC6 TEC at Patrick AFB, FL
0500 UT (0000 LT) 1520 UT (1020 LT)
Absolute TEC processing
• Correct Pseudorange for local multipath
• Fix cycle slips and outliers in carrier phase data
• Phase-to-pseudorange leveling
• Differential code bias correction
Chung-Li COSMIC TBB/CERTO
TEC & Elevation Angle
Profile retrieval method
TEC = solid – dashed [Schreiner et al., 1999]
ptop
rN (r )
p
r p
T EC( p) = 2
2
2
dr
• Inverted via onion-peeling approach to obtain
electron density N(r)
• Assumption of spherical symmetry
TIP passes near Kwajalein
14 Sep 2006, 2100 LT
structure
observed
Improved Measurements of Ionospheric Layer Height
Using Radio Beacon Data
Courtesy of L.J. Nickish (NWRA)
5% Error
0.3% Error
August 14, 1997
at 01:04UT
Beacon
Satellite
Orbit
Beacon
Receivers
OTHR Only
OTHR + TEC Inversion
Ionosphere Limits OTHR Target Tracking to ~ 10 km
Radio Beacon Data Reduces Error to < 2 km
COSMIC Soundings in 1 Day
COSMIC
Radiosondes
Sec 3, Page 10
Atmospheric Coupling in the Ionosphere
Non-Migrating Tide 4-cell Pattern
14 Sep 2006 (near Solar Minimum)
GUVI Composite
Image
135.6-nm (green)
130.4-nm (blue)
LBH short (red)
0030 LT at
equator
GUVI sensitivity
threshold 10-20
Rayleighs
TIP 135.6-nm
2100 LT at
equator
TIP sensitivity
threshold ~0.002
Rayleighs
Counts
= 20 Rayleighs
Large depletion
over Africa
How Will the Tiny Ionospheric Photometer
Measurements Be Used?
• Primary Goal: Provide Accurate
Characterization of Ionospheric
Electron Density Gradients
– Inaccuracies in GPS occultation
measurements of electron density due to
gradients
– TIP measurements will be used to
correct for gradients
• Secondary Goals:
– Location of auroral oval – TIP measured
135.6 nm emission produced by aurorae
– Location of Appleton peaks – infer
ionospheric dynamics
– Detection of Equatorial Spread-F –
specify instability conditions
– Add to Ionospheric & Thermospheric
Climatology Databases
COSMIC1 TEC at Patrick AFB, FL
1520 UT (1020 LT) 0500 UT (0000 LT)
COSMIC5 TEC at Patrick AFB, FL
0800 UT (0300 LT) 1900 UT (1200 LT)