MODIS ProtoFlight Model (PFM) Relative Spectral Response (RSR) Readme File
Outline:
1.0 Summary of PFM RSR Releases
2.0 RSR Look-Up Table (LUT) I (in-band RSRs as used in L1B V2.2; corrected)
3.0 RSR Reference Table (all data; in-band + OOB; merged and corrected)
4.0 Reference Summary of RSR Center Wavelengths (CWs) and Bandwidths (BWs)
5.0 Notes for the L1B Look-Up-Table (LUT)
6.0 Notes for the RSR Reference Table
7.0 References
1.0 Summary of PFM RSR Releases
Original Release: Dated 2-24-97
Rev A: Dated, 3-6-98
Rev B: Dated, 8-8-98
Rev C: Dated, 4-30-99
General Discussion
PFM RSR Rev. C release incorporates the latest data merging and correction results.
Notes in sections 5.0 and 6.0, together with material contained in the references called
out in section 7.0 discuss the RSR raw data correction, interpolations, and merging steps.
It is intended that this release will be the pre-launch version of the RSR LUT used in the
L1B V2.2 Calibration production code. This release contains two (2) versions of the RSR
tables:
L1B Look-Up-Table (LUT) contains the In-band RSRs for each of the channels for 36
spectral bands. In-band is defined as the RSR values between the 1% response
wavelengths, e.g., 1% low and 1% high. The results will be incorporated into the MCST
L1B V2.2 Calibration processing code. It should be noted that the RSR data presented for
PFM Band 7, were taken from the FM1 Band 7 measurements, due to the fact that the
PFM Band 7 in-band RSR measurements were saturated in the peak response region,
preventing accurate determination of the PFM RSR.
The RSR Reference Table contains the merged In-band and Out-of-Band Dispersive
(OOB-D) data sets. These RSRs contain all measured data, including optical crosstalk
features of the PFM and provide an overview of all measured spectral response. It should
be noted that V2.2 of L1B will incorporate data correction, i.e. subtraction routines to
partially reduce OOB crosstalk for SWIR bands 5,6 and PC bands 32-36.
The results presented in L1B Look-Up-Table (LUT) have been corrected for all known
biases and aberrations. At a top level these corrections include:
1) Correction for the GSE Spectroradiometer Measurement Apparatus (SpMA) out-ofplane spectral aberrations (AKA, the smile effect).
2) SpMA wavelength calibration offsets
3) Atmospheric path absorption corrections
4) Window absorptions
5) Tfpa (79K->83K) corrections
The results presented in RSR REFERENCE TABLE have also been corrected for all
known biases and aberrations. Out-of-Band Dispersive (OOB-D) low spectral resolution
measurements have been merged with the high spectral resolution In-band RSR data, for
Bands 1-28, following data normalization results provided by SBRS. PFM OOB data are
not available for Bands 29-36. For this reason, FM1 OOB-D are merged with the PFM
In-band RSRs to provide some characterization of the OOB regions for these bands.
Since the PFM and FM1 spectral filters were purchased together, there is some basis for
this fill-in approach. Differences between PFM and FM1 dichroics may exist, and could
in-principle affect the OOB-D regions somewhat.
Table A presented in Section 4.0 of this file, summarizes the integrated Center
Wavelength (CW) and integrated centroid Bandwidth (BW) for each of the MODIS PFM
bands. These results were obtained by integration of the channel-averaged RSRs, i.e., the
RSRs from each channel were added, and then divided by the number of channels.
RSR Corrections Algorithm Flow Chart
A flow diagram of all correction steps taken is provided with this distribution of files in
PDF file format. This file can be found in the
/pub/permanent/MCST/PFM_L1B_LUT_4-12-98 directory of the ftp.mcst.ssai.biz ftp
server.
Format: Table A (In-Band; corrected))
Band Channel
20
1
.
.
.
.
20
1
.
.
.
.
20
1
.
.
.
.
20
2
.
.
.
.
.
.
.
.
Wavelength (nm) RSR
3621.40
0.01 (start)
.
.
.
.
3851.58
1.00 (peak)
.
.
.
.
3961.00
0.01 (stop)
.
.
.
.
3621.40
0.01
.
.
.
.
.
.
.
.
Format: Table II (All data; Merged and corrected)
Band
20
.
.
20
.
.
20
.
.
20
.
.
Channel
1
.
.
1
.
.
1
.
.
2
.
.
Wavelength (nm)
RSR
1100.00
1.7743e-06 (start)
.
.
.
.
3851.58
1.0
(peak)
.
.
.
.
5400.00
1.4691e-05 (stop)
.
.
.
.
1100.00
1.7341e-06
.
.
.
.
4.0 Center Wavelength and Bandwidths for all MODIS bands
BW and CW are calculated by integrating over the response between the lower 1%
response wavelength and the upper 1% response wavelength. The all values in the chart
below are band averaged.
Band CW (nm)
(1%/1%)
BW (nm)
(1%/1%)
--------------------------------------------------------------------------------B1 646.5
41.8
B2 856.7
39.4
B3 465.6
17.6
B4 553.7
19.7
B5 1241.9
24.5
B6 1629.1
29.7
B7 2114.3
52.9
B8 411.8
11.8
B9 442.1
9.7
B10 486.9
10.6
B11 529.7
11.8
B12 546.8
10.4
B13 665.6
10.1
B14 676.7
11.4
B15 746.4
10.0
B16 866.2
15.5
B17 904.1
35.7
B18 935.3
B19 936.1
B26 1382.0
B20 3788.2
B21 3992.1
B22 3971.9
B23 4056.7
B24 4473.2
B25 4545.4
B27 6765.4
B28 7336.7
B29 8528.8
B30 9734.4
B31 11018.6
B32 12032.5
B33 13365.1
B34 13683.5
B35 13913.3
B36 14195.7
13.7
46.3
36.4
182.6
85.7
88.2
87.8
93.7
94.3
254.6
325.3
369.2
300.6
510.3
493.5
306.5
322.4
333.6
268.8
5.0 Notes on Look-Up Table
I-1: A correction be made to all grating 4 bands based on the shift detected between the
known location of the C02 absorption feature and the perceived notch in the band 35
RSR. Currently our best knowledge of the C02 feature minimum is at 13876 according a
LOTRAN model run. The number of RSR points in the band 35 RSR near the C02
absorption feature is limited, so the exact location of the C02 notch can not be
determined.
I-2: Due to SpMA wavelength aberration correction procedure used, the wavelengths set
will be different from channel-to-channel. Also all channels have identically the same
center wavelength value due to the SpMA wavelength correction.
I-3: The profile of band 35 relative spectral response profile was adjusted in order to
remove the effects caused by the C02 absorption feature. A simple linear fit was used in
order to replace badly affected points in the C02 absorption region.
I-4: PFM Bands 29-36 were taken under ambient conditions using the Bench Test Cooler
(BTC) which held the LWIR focal plane and the filter assembly at 79.6K to 79.9K.
Temperature shifts have been applied to bands 27-36. FM1 shifts were determining the
shift in center wavelength measured at NLT and 83K for each band for SWIR, MWIR
and LWIR bands. FM1 shift data was fit to a linear function in order to determine the
slope of the correction to apply to PFM RSRs per band.
6.0 Notes on the RSR Reference Table
I-1: No valid out-of-band data was available for PFM bands 29-36. In these cases PFM
in-band data was merged with FM1 out-of-band data. Please note that significant PC
optical crosstalk does exist for bands 32-36, which is not reflected in these out-of-band
data sets borrowed from FM1. All other MODIS bands have valid PFM out-of-band
RSRs included in this data set.
I-2: The wavelength increments differ between IB and OOB regions, and from band-toband.
I-3: The channel-dependent RSRs were merged with the average OOB RSRs, since the
OOB measurements were generally noise limited, and therefore the average OOB for that
band is believed to be a better representation of the real performance. See Note 4 for two
exceptions.
I-4: Wherever possible, the average OOB RSR is merged with the channel dependent Inband RSR. However, for band 3 - channel 7 the OOB RSR data was significantly out-offamily from the other 19 channels and therefore the as-measured OOB RSR for this
channel was merged with the In-band RSR for that channel. Likewise, Band 16 - Channel
10 out-of-band RSR data was significantly out-of-family from the other 9 channels, and
therefore the as-measured OOB RSR for this channel was merged with the In-band RSR
for that channel.
I-5: OOB RSRs measured data points near the spectral band pass regions (the wings of
the IB RSR) are misleading. For Bands 23,24, and 25 we extrapolated the IB RSRs down
to the 0.001 RSR level to more accurately characterize the true instrument response in the
wing regions near the band pass region.
Relative Spectral Response File locations
The described files are available in ASCII format by anonymous ftp on ftp.mcst.ssai.biz
in the /pub/permanent/MCST/PFM_L1B_LUT_4-30-99 directory.
A flow chart describing RSR wavelength correction methodology is available in this
directory called RSR_methodology.ppt (MS PowerPoint format).
The locations for the PFM L1B RSR Look-up-tables is:
/pub/permanent/MCST/PFM_L1B_LUT_4-30-99/L1B_RSR_LUT
A PDF file called pfm-in-band-rsr.pdf contains plots for all bands.
PDF files containing plots of this data will be available also in these directories.
The locations for the PFM Reference (in-band and our-of-band merged) data sets is:
/pub/permanent/MCST/PFM_L1B_LUT_4-30-99/Reference_RSR_Dataset. A PDF file
called pfm-oob-rsr.pdf contains plots for all bands.
7.0 References:
Bands PFM Calibration Launch Readiness Review, Dorman, Godden February 3/99,pgs
7-1 to 7-94
MODIS Science Team Meeting, Relative Spectral Response, T. Dorman, G. Godden
October 24,97,pgs 4-1 to 4-65
Spectral calibration gradient along SpMA slits, J.B. Young, 3/18/97,PL3095-N006345
Reflective Bands Relative Spectral Responses (RSR) Along Track Variability,T.
Dorman, G. Godden, June 13,1997