1. © The Aerospace Corporation 2010 Radio Occultation Sensor Observations of Ionospheric Scintillation P. R. Straus 1, C. Carrano 2, R. Caton 3, K. Groves 3, and R.L. Bishop 1 The Aerospace Corporation 2 Boston College 3 Air Force Research Laboratory

2. 2 Overview CORISS-Radar-Theory evaluation of RO scintillation observation Calculation of S4 “Proxy” S4 indices Ground UHF/RO scintillation comparison

3. Tangent Point Track Apex Altitude 300-400 km C/NOFS Orbital Track 21 Apr 2009 10:09 UT CORISS/ALTAIR Geometry

4. Coherent Returns from ALTAIR & CORISS SNR ALTAIR indicates location of small-scale (40cm) irregularities relative to the CORISS tangent point track. CORISS detects ionospheric irregularities only within F region, while high sensitivity of ALTAIR reveals structure at slightly lower altitudes. Mean scattering location is slightly westward of the CORISS tangent point track. CORISS occultation tangent points CORISS SNR Bottomside Max Height 10

5. Assume weak scattering: Break frequency Fresnel null frequencies Given propagation orthogonal to B, then Yields d s ~ 630 km (t.p. is ~500 km) Determine irregularity strength, region size, spectral slope, & BG density profile from ALTAIR, SCINDA & CORISS measurements where d is C/NOFS-GPS distance PRN 16 CORISS Observations & Simulation CORISS Multiple Phase Screen Simulation

6. 15 MPS Simulation CORISS Multiple Phase Screen Simulation of CORISS Data

7. Proper Calculation of the S4 Index What sample rate should be employed? How long a data segment should be analyzed? The answer depends on the Fresnel frequency –Optimally, one should observe at a frequency substantially above f Fresnel and calculate S4 over a sample interval 10  longer than 1/f Fresnel –For occultation data 50 Hz observations are adequate with a 10 second sample interval RO data does not support calculation of S4 over a 1-second interval Data must also be detrended prior to calculating S4 where P i is the receiver power

8. “Proxies” for S4: S RO (1s) Calculated from MR (1 Hz) C/A SNR observations 1 Hz Data 50 Hz Data PRN27 @2009/03/30 05:10:00 S RO(1s) (31 s) S4 (10 s) C/A SNR S RO(1s) S4 (10 s) All profiles with max(S RO(1s) ) > 0.5

9. Summary of CORISS (L-Band)/SCINDA (UHF) Comparisons

10. “Proxies” for S4: UCAR S4 (COSMIC) Calculated from on-board 50 Hz SNR variance collected at 1 s cadence S4 (1s) UCAR S4 (10s) C/A SNR S4 (1 s) PRN27 @2009/03/30 05:10:00 S4 (10 s) S4 (10s) UCAR S4 (10s) All profiles with max(S RO(1s) ) > 0.5

11. 11 Summary CORISS high rate observations of scintillation are in the process of being validated through ground/theory comparisons S RO(1s) calculated from 1 Hz SNRs generally under-predicts S4, but is fairly representative of S4 characteristics most of the time –The lower noise floor is useful for certain types of analysis UCAR (COSMIC) 1-second S4 index is not valid, but the UCAR approach to S4 determination can be made to work quite well if calculations are extend over a larger time interval (10 s)

12. 12 Simulation of Scintillation in a Limb Viewing Geometry

13. 13 Single Bubble Simulation

14. 14 Multi-Bubble Simulation