CDAAC Ionospheric Products

Transcription

1 CDAAC Ionospheric Products Stig Syndergaard COSMIC Project Office COSMIC retreat, Oct 13 14, 5

2 COSMIC Ionospheric Measurements GPS receiver: { Total Electron Content (TEC) to all GPS satellites in view Ionospheric radio occultations (profiles) & scintillations Tiny Ionospheric Photometer (TIP): Ultra-violet emission from ionosphere Tri-Band Beacon (TBB): TEC & scintillations on satellite-to-ground links

3 COSMIC Ionospheric Measurements Total Electron Content measurements: High-resolution (1 Hz) TEC to all GPS satellites in view at all times Can track up to 1 GPS satellites at the same time (9 aft + 4 fore) Useful for global ionospheric tomography and data assimilation

4 COSMIC Ionospheric Measurements Ionospheric GPS occultation measurements: High-resolution (1 Hz) occultation TEC below orbit altitude Ionospheric electron density profiles from orbit altitude and down Ionospheric scintillations using the two limb antennas (5 Hz)

5 COSMIC Ionospheric Measurements Tiny Ionospheric Photometer measurements: Emission (1356 Å) due to recombination of oxygen ions and electrons Nadir intensity along sub-satellite track proportional to N e dz High quality data on night-side uncertainty about day-side quality

6 COSMIC Ionospheric Measurements Tri-Band Beacon measurements: Radio signals transmitted from COSMIC at 15, 4, and 167 MHz TEC between the COSMIC satellites and chains of ground receivers Amplitude and phase scintillations on the satellite-to-ground links

7 Ionospheric Data from CHAMP, Oct TECU 5 Elevation angle (deg) : UT : UT 3: UT 4: UT 5: UT 4 7: UT 8: UT 9: UT 1: UT 11: UT 1: UT 4 CHAMP Langmuir Probe CHAMP Occultation data Altitude (km) : UT 1: UT : UT 3: UT 4: UT 5: UT 6: UT 7: UT 8: UT 9: UT 1: UT 11: UT 1: UT :39 UT :45 UT 1:5 UT 1: UT 1:35 UT :33 UT 1 3 Electron density (16cm-3). :44 UT :56 UT 3:33 UT 3:41 UT 3:51 UT 4:1 UT 1 3 Electron density (16cm-3). 4: UT 4:7 UT 4:4 UT 5:4 UT 5:14 UT 5:33 UT 1 3 Electron density (16cm-3). 5:49 UT 6:6 UT 6: UT 6:34 UT 6:4 UT 6:58 UT 1 3 Electron density (16cm-3). 7:4 UT 7:35 UT 7:5 UT 8:7 UT 8:37 UT 9:17 UT 1 3 Electron density (16cm-3). 1:9 UT 1:31 UT 11:33 UT 11:38 UT 1: UT 1:8 UT 1 3 Electron density (16cm-3) Altitude (km) Electron density (16cm-3) 6: UT Electron density (16cm-3) : UT

8 Method of Deriving Orbit Electron Density COSMIC LEO GPS Measurements available before occultation (dashed lines) TEC = solid minus dashed TEC(r) r orb N e (r orb ) r orb r Fit a straight line to ( TEC) for the uppermost few km

9 Occultation Versus in-situ Electron Density Electron density (cm -3 ) - Occultation data 1e+7 1e RMS = cm -3 Correlation = e+6 1e+7 Electron density (cm -3 ) - Langmuir Probe

10 Processing Steps Toward Absolute TEC 8 Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. P - P1 (code) L1 - L (phase) 6 Range difference (m) Time of day (sec)

11 Processing Steps Toward Absolute TEC 8 Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. > Cycle slip detection and correction P - P1 (code) L1 - L (phase) 6 Range difference (m) 4 Cycle slip Time of day (sec)

12 Processing Steps Toward Absolute TEC 8 Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. > Cycle slip detection and correction P - P1 (code) L1 - L (phase) 6 Range difference (m) Time of day (sec)

13 Processing Steps Toward Absolute TEC 8 Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. > Cycle slip detection and correction > Quality Control P - P1 (code) L1 - L (phase) 6 Range difference (m) 4 Not sure Time of day (sec)

14 Processing Steps Toward Absolute TEC 8 Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. > Cycle slip detection and correction > Quality Control P - P1 (code) L1 - L (phase) 6 Range difference (m) Time of day (sec)

15 Processing Steps Toward Absolute TEC 8 6 Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. > Cycle slip detection and correction > Quality Control > Adjusting phases to codes P - P1 (code) L1 - L (phase) Range difference (m) Time of day (sec)

16 Processing Steps Toward Absolute TEC 8 6 Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. > Cycle slip detection and correction > Quality Control > Adjusting phases to codes P - P1 (code) L1 - L (phase) Range difference (m) Time of day (sec)

17 Processing Steps Toward Absolute TEC 8 6 Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. > Cycle slip detection and correction > Quality Control > Adjusting phases to codes > Correcting for GPS Differential Code Bias P - P1 (code) L1 - L (phase) Range difference (m) Time of day (sec)

18 Processing Steps Toward Absolute TEC 8 6 Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. > Cycle slip detection and correction > Quality Control > Adjusting phases to codes > Correcting for GPS Differential Code Bias P - P1 (code) L1 - L (phase) Range difference (m) Time of day (sec)

19 Processing Steps Toward Absolute TEC Range difference (m) Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. > Cycle slip detection and correction > Quality Control > Adjusting phases to codes > Correcting for GPS Differential Code Bias > Correcting for CHAMP Differential Code Bias P - P1 (code) L1 - L (phase) Time of day (sec)

20 Processing Steps Toward Absolute TEC Example of CHAMP - GPS data arc (PRN 3) on Oct 9, 3. Total Electron Content (TECU) > Cycle slip detection and correction > Quality Control > Adjusting phases to codes > Correcting for GPS Differential Code Bias > Correcting for CHAMP Differential Code Bias > Converting to Total Electron Content Absolute TEC Time of day (sec)

21 LEO Differential Code Bias estimation A B Weighted average of paired observations Model independent Assumption: TEC A sin θ A = TEC B sin θ B Restrictions: Both θ A and θ B > 45 Vertical TEC < 3 TECU DCB leo = (sin θb sin θ A )( TEC A sin θ A TEC B sin θ B ) (sin θb sin θ A )

22 LEO Differential Code Bias estimation A B Weighted average of paired observations Model independent Assumption: TEC A sin θ A = TEC B sin θ B Restrictions: Both θ A and θ B > 45 Vertical TEC < 3 TECU DCB leo = (sin θb sin θ A )( TEC A sin θ A TEC B sin θ B ) (sin θb sin θ A )

23 LEO Differential Code Bias estimation A B Weighted average of paired observations Model independent Assumption: TEC A sin θ A = TEC B sin θ B Restrictions: Both θ A and θ B > 45 Vertical TEC < 3 TECU DCB leo = (sin θb sin θ A )( TEC A sin θ A TEC B sin θ B ) (sin θb sin θ A )

24 CHAMP Differential Code Bias CHAMP DCB (TECU) next day prediction Day of year, 3 Based on simple assumptions (e.g., azimuthal symmetry above LEO) Single day estimates based on 4 hr average next day prediction (for near real-time processing) based on smoothing over 5 days For COSMIC there will be 6 DCBs to solve for

25 CHAMP Ionospheric Scintillation Map

26 Latest Progress on TIP Data Processing Code to get TIP pointing location from attitude is completed Awaiting code from NRL for converting raw counts to radiances TIP pointing track Sub-satellite track latitude (deg) longitude (deg)

27 Status and Plans for COSMIC Total Electron Content measurements Plans: Cycle-slip detection and correction, Quality control, and Differential Code Bias calibration Status: Prototype working for CHAMP data not yet integrated in CDAAC processing system Ionospheric GPS occultation measurements Plans: Reducing effects from horizontal gradients in profile retrievals using a model (e.g., GAIM) Status: Profiles derived via Abel inversion Scintillation maps not yet integrated in CDAAC system Tiny Ionospheric Photometer measurements Plans: Providing radiances derived from raw data (counts) as well as pointing direction Combining TIP data and GPS occultation data for in-plane occultations (Naval Research Lab) Status: TIP pointing location code is in place Anticipate to get radiance code from NRL soon Tri-Band Beacon measurements Plans: Plans regarding processing of TBB data are not in place One TBB receiver may be installed on the top of the roof at UCAR CDAAC will process data from this one Status: Ongoing work to install receiver chains in various countries all over the world (NRL)