1. SOFIE Overview
Mark Hervig
Larry Gordley

2. PMC Interference (signal fraction)
SOFIE
Solar Occultation
8 channel differential radiometer
16 bands, 290 nm - 5 m wavelength
Coverage from  latitude
Retrieval
Precision
Required / CBE
Altitude Range
(km)
PMC Interference (signal fraction) T
5 / 3.5 K
1 - 95 0% O3
100 / 7 ppbv
50%
H2O
0.6 / 0.04 ppmv
CO2
10 / 7 ppmv
CH4
50 / 38 ppbv
90% NO
1.0107 / 1.1107 cm-3
20%
PMCs
V: 510-5 / 1.810-5 km-1
V: 510-5 / 1.110-7 km-1
cloud -

3. SOFIE Changes
The SOFIE steering mirror assembly (SMA) failed when vibrated above design limits during S/C integration & test in June 2006.
The steering mirror was replaced with a rigid mirror.
The impact:
1) SOFIE pointing now relies on the spacecraft AC system.
AIM requirements are met.
2) Complete calibration and TVAC testing were performed in November 2006.
Confirmed that nothing else was damaged.
Small changes in mirror reflectance spectra resulted in little or no change.

4. SOFIE Pointing SOFIE Steering Mirror Assembly provided:
- Ability to point and hold FOV at sun center during entire occultation
- Agility to accomplish calibration maneuvers during an event
Using the spacecraft to point SOFIE provides:
- Sufficient stability to achieve required science objectives.
- Capability to accomplish calibration maneuvers, though some will require multiple events and increased demand from flight operations.
The SOFIE sun sensor remains functional and precise: sub-arcsec knowledge

5. SOFIE Pointing Then and Now
The steering mirror provided
Lockdown: sun center, < 1 arcsec uncertainty
FOV drift: <1 arcsec during an occultation.
Pointing stability is important
because solar intensity
changes across the disk.
The spacecraft provides
Lockdown: sun center, <2.5 arcmin uncertainty
FOV drift: <12 arcsec through PMC altitudes
FOV
exaggerated drift

6. SOFIE Errors Related to Pointing
Effects of FOV lockdown uncertainty and drift were characterized by combining
Spacecraft pointing errors & SOFIE signal simulations
Signals simulated by convolving 2D FOV over 2D solar source.
Drift-induced V signals were determined as worst case for:
All lockdowns with 2.5 arcmin of center
12 arcsec drift in all directions from lockdown.
Drift-induced V signals were then corrected using:
Sun sensor pointing knowledge (0.88 arcsec 1 error)
Measured limb darkening curve (w/ appropriate noise)
The remaining signal error is now carried in SOFIE performance estimates.
Note: expected steady drifts can be removed with lower uncertainties by fitting and extrapolating in time.

7. Impact of Spacecraft Pointing Drift on SOFIE SNR
Chan.
Band / Target
Center Wavelength
(m)
V SNR Required / CBE Margin (random)
Worst case induced V uncertainty
(quasi-systematic in noise units)
12 arc-sec drift in any direction
from lockdown at 2.5 arcmin*
Margin after RSS of random + systematic 1
1 / O3 s
0.291
1.0e4 / 210.9
0.08
12.8
2 / O3 w
0.330 2
3 / PMC s
0.867
1.0e6 / 5.9
1.79
0.6
4 / PMC w
1.04 3
5 / H2O w
2.46
2.5e4 / 16.6
0.02
15.7
6 / H2O s
2.62 4
7 / CO2 s
2.79
3.0e5 / 1.4
0.19
1.3
8 / CO2 w
2.94 5
9 / PMC w
3.06
1.0e5 / 3.0
0.16
2.7
10 / PMC s
3.12 6
11 / CH4 s
3.38
4.0e5 / 1.3
0.23
12 / CH4 w
3.48 7
13 / CO2 s
4.32
4.0e5 / 1.5
0.17
1.5
14 / CO2 w
4.65 8
15 / NO w
5.01
3.0e5 / 0.9
0.26
0.9
16 / NO s
5.32
*Lockdown was moved within a radius of 2.5 arcmin and the signal change for 12 arcsec drift (over 10 seconds / 25 km) was calculated. Numbers shown are the worst case for all possible lockdowns. Note: the drift induced dV signal uncertainty is the error in the corrected signal considering a regression to the signal change vs FOV drift, the measurement noise (from calibration), and the pointing error (from calibration).
This analysis captures all of the errors and is our CBE.

8. Predicted SOFIE Retrieval Performance
Retrieval performance meets or exceeds AIM science requirements
Geophysical Parameter
Precision
Required / SMA Margin / Rigid Mirror Margin
Altitude Range, km
Required / Current
Vertical Resolution, km
NIR cloud extinction*
5x10-6 km-1 / 5.9 / 0.6
78 – 85 / 75 – 90
 3 / 1.5
IR cloud extinction
5x10-5 km-1 / 3.0 / 2.7
temperature
5 K / 1.5 / 1.4
70 – 90 /
O3 mixing ratio
0.1 ppmv / 50 / 12.8
78 – 90 /
H2O mixing ratio
0.6 ppmv / 17 / 14.0
78 – 90 /
CO2 mixing ratio
10 ppmv / 1.5 / 1.4
80 – 100 /
CH4 mixing ratio
0.05 ppmv / 1.3 / 1.4
30 – 90 /
NO mixing ratio
107 cm-3 / 0.9 / 0.9
80 – 95 /
 5 / 3
*This measurement is not an AIM Level 1 science requirement

9. On-Orbit Calibration with S/C Pointing
In-flight calibrations are accomplished by directing the FOV through various maneuvers:
Routine Calibration (every event):
Solar scan to characterize the solar limb darkening curve (SLDC)
Periodic Calibration (~monthly):
Nonlinearity, Sun sensor FPA flat field, Boresight, FOV mismatch
Difference signal gain, Low-pass filter response
The spacecraft can perform the required maneuvers.
Some calibrations will now require statistical analysis.
Elevated but realistic requirements on SOFIE operations and Mission operations.
(Greg has more on this)

10. Recent SOFIE Calibration
SOFIE underwent final TVAC testing and Calibration in Nov 2006.
All items characterized at nominal operating temperature:
Noise
Gain
Nonlinearity
FOV, knife edge & point source
RSR, in-band & select out-of-band
Sun sensor

11. SOFIE Calibration: Signal-to-Noise
SOFIE noise levels were characterized using measurements taken with the chamber aperture closed.
Comparisons with past data indicate little or no change.
SNR margin =
(215  V gain / V) / (SNR required)
No Change, all channels have margin > 1, except 8.
Chan.
Band / Target
V SNR Margin
Oct 2005
Nominal
Feb 2006
Nov 2006 1
1 / O3 s
146.2
148.1
210.9
2 / O3 w 2
3 / PMC s
5.2
5.8
5.9
4 / PMC w 3
5 / H2O w
15.7
17.4
16.6
6 / H2O s 4
7 / CO2 s
1.3
1.4
8 / CO2 w 5
9 / PMC w
3.0
10 / PMC s 6
11 / CH4 s
1.2
12 / CH4 w 7
13 / CO2 s
1.5
1.7
14 / CO2 w 8
15 / NO w
0.9
16 / NO s

12. SOFIE Calibration: RSR
In-Band RSR 50% Response Limits
Band
Measurement
Specification
Jan (PER)
Nov 2006
Cuton - Cutoff (m)
Cuton-Cutoff (m) 1
O3 Strong – – – 2
O3 Weak – – – 3
Particle Strong – – – 4
Particle Weak –
1.015 – 1.059 5
H2O Weak
2.427 – 2.475
2.436 – 2.488 6
H2O Strong
2.577 – 2.632
2.592 – 2.644
2.592 – 2.643 7
CO2 Strong
2.740 – 2.794
2.758 – 2.813 8
CO2 Weak
2.907 – 2.967
2.910 – 2.968 9
3.030 – 2.091
3.035 – 3.094
3.038 – 3.097 10
3.160 – 3.226
3.152 – 3.219
3.155 – 3.221 11
CH4 Strong
3.333 – 3.401
3.345 – 3.422
3.347 – 3.424 12
CH4 Weak
3.472 – 3.546
3.445 – 3.514
3.447 – 3.516 13
4.255 – 4.444
4.219 – 4.428
4.221 – 4.429 14
4.630 – 4.740
4.581 – 4.712
4.583 – 4.714 15
NO Weak
4.951 – 5.051
4.959 – 5.053
4.962 – 5.055 16
NO Strong
5.263 – 5.376
5.236 – 5.396
5.238 – 5.399

13. SOFIE Calibration: Nonlinearity
Oct 2005
Comparison of nonlinearity calibration data from Oct 05, Feb 06, and Nov 06 show consistent results. Example plots for band 8 are shown here.
Feb 2006
Nov 2006

14. SOFIE Calibration: FOV
MIC1 rectangular aperture was scanned across the SOFIE aperture in discrete steps. The derivative of measured response yields the FOV response curve.
Requirements (FWHM):
EL: 1.8 arcmin
Band 3-16 Averages, Feb 2006:
EL: 1.90 arcmin
Band 3-16 Averages, Nov 2006:
EL: arcmin
Note: the Nov 2006 cal was done at higher spatial resolution than previously. Changes are small and within the calibration uncertainty.
Chan.
Band / Target
EL Dimension (arcmin, FWHM)
Feb 2006, day 51
Nov 2006 1
1 / O3 s
1.86
2 / O3 w
1.96 2
3 / PMC s
1.83
4 / PMC w
1.77
1.85 3
5 / H2O w
1.73
1.65
6 / H2O s
1.87
1.68 4
7 / CO2 s
2.00
1.80
8 / CO2 w
1.99
1.76 5
9 / PMC w
1.70
10 / PMC s
1.81
1.59 6
11 / CH4 s
2.03
1.93
12 / CH4 w
1.66 7
13 / CO2 s
2.02
14 / CO2 w
2.07 8
15 / NO w
1.97
16 / NO s
1.98

15. SOFIE Calibration: Sun Sensor
The sun was viewed for several minutes on 6 Nov The SOFIE sun sensor measured the image location, and stayed in fine track for most of the test.
Without the SMA, the solar image drifted across the FPA. Drift was removed using a linear trend, and the tracking precision was estimated as the standard deviation of the mean at 2 Hz. Example analysis of elevation data are shown at right.
Results from Nov 2006:
Elevation precision = 0.70 arssec.
Azimuth precision = 0.54 arssec.
Results from Nov 2005:
Elevation precision = 0.32 arssec.
Azimuth precision = 1.68 arssec.

16. November 2006 Calibration Summary
Data collected to address all critical performance aspects
Results indicate excellent system performance & little or no changes
System Functionality
Requirement
November 2006 Calibration Results
Signal to Noise
Margin > 1
No Change
Measured margin > 1 (except NO channel, 0.9)
Response Nonlinearity
 < 0.5%
No change
< 0.5% calibration uncertainty on all bands
V Gain
As specified
Radiometer Gain *
Small (5%) changes at short wavelengths
(as expected due to new mirror reflectance spectra)
Background Signals
N/A
RSR - Bandpass
RSR – Out of Band Energy
 Desired < 1%
FOV
Pointing Knowledge
 < 1 arcsec in elevation
Slight Improvement (< 1 arcsec in azimuth & elevation)
* Does not affect science. Balance adjustment can accommodate changes of 100% or more before science is impacted.

17. Science Products / Post processing
PMC identification:
Find PMCs in SOFIE profiles using threshold approach
Determine cloud heights: top, base, & peak
Status: baseline version complete
Issues: may require sophistication such as spectral identification
PMC ice mass:
Determine ice mass content in PMCs (direct proportionality to IR extinction)
Status: complete
Issues: small dependence on particle shape & refractive index
PMC size distribution retrievals:
Retrieve a 3-parameter size distribution (lognormal or gaussian)
Issues: choice of refractive indices, particle shape / aspect ratio…

18. (Backup Slides Follow)
Summary
Testing indicates that damage to SOFIE was limited to the steering mirror.
Calibration shows little or no change in SOFIE performance.
Spacecraft pointing allows SOFIE measurements to meet AIM requirements.
(Backup Slides Follow)

19. SOFIE Pointing l1 l2 Solar intensity varies spatially across the disc
The strength and shape of this variation is a function of wavelength
Radiometer signals vary simply with spatial variations in the solar limb darkening (SLD) curve
Difference signals are affected by
Differences in the SLD at each wavelength.
FOV missmatch between band pairs S
Radiance
Distance Along Solar Disc l1 l2 Ro R1 R2
2 < 1
For S: Ro - R2 >> Ro - R1

20. SOFIE Status Instrument: SOFIE is integrated on the spacecraft.
S/C TVAC is complete.
S/C vibe is complete.
No issues or non-conformances
Data Processing Software (Retrievals):
Level 0:
Level 1:
Level2:

21. Outline Overview of SOFIE changes SOFIE status Calibration results
Predicted retrieval performance
Summary

22. SOFIE Nonlinearity Calibration
Detector response nonlinearity has been calibrated numerous times.
The CSM flight ND filter was absent in the Oct 2005 results, allowing the entire dynamic range to be sampled. The Oct 2005 results are therefore considered our current baseline.
The ND filter was in place for later results, allowing about 1/3 of the dynamic range to be covered.
Changes from the baseline Oct 2005 results are small, and generally within the calibration uncertainty.
Chan.
Band / Target
Nonlinearity (%)  error* (%)
at 215 counts
Oct 2005
Feb 2006
Nov 2006 3
5 / H2O w
5.9  0.3
4.7  1.3
4.2  1.2
6 / H2O s
5.1  0.3
6.1  1.0
6.9  0.7 4
7 / CO2 s
31.4  0.2
33.4  0.8
35.7  0.5
8 / CO2 w
28.0  0.4
31.2  0.7
31.2  0.3 5
9 / PMC w
2.6  0.2
6.5  0.9
7.7  0.7
10 / PMC s
5.3  0.2
6.5  0.7
4.4  0.4 6
11 / CH4 s
5.7  0.2
8.0  0.6
7.1  0.3
12 / CH4 w
8.4  0.2
10.5  0.8
8.3  0.4 7
13 / CO2 s
16.4  0.4
19.1  0.8
17.4  0.2
14 / CO2 w
10.3  0.3
12.1  0.5
12.3  0.2 8
15 / NO w
6.3  0.2
10.4  0.5
8.5  0.2
16 / NO s
7.2  0.2
11.1  0.5
9.7  0.2
*The nonlinearity error is the associated signal error when viewing the unattenuated sun.

23. Impact of Spacecraft Pointing Drift on SOFIE SNR
HALOE demonstrated steady time dependent drifts, if this is the case for SOFIE…
Chan.
Band / Target
Center Wavelength
(m)
V SNR Required / CBE Margin (random)
Margin IF
drift-induced noise is a steady function of time
Baseline Margin Including drift-induced noise 1
1 / O3 s
0.291
1.0e4 / 210.9
27.6
12.8
2 / O3 w
0.330 2
3 / PMC s
0.867
1.0e6 / 5.9
1.4
0.6
4 / PMC w
1.04 3
5 / H2O w
2.46
2.5e4 / 16.6
16.2
15.7
6 / H2O s
2.62 4
7 / CO2 s
2.79
3.0e5 / 1.4
1.3
8 / CO2 w
2.94 5
9 / PMC w
3.06
1.0e5 / 3.0
3.0
2.7
10 / PMC s
3.12 6
11 / CH4 s
3.38
4.0e5 / 1.3
12 / CH4 w
3.48 7
13 / CO2 s
4.32
4.0e5 / 1.5
1.5
14 / CO2 w
4.65 8
15 / NO w
5.01
3.0e5 / 0.9
0.9
16 / NO s
5.32