B. Carol Johnson, Maritoni Litorja, Joel B. Fowler, Eric L. Shirley, Robert A. Barnes, and James J. Butler, "Results of aperture area comparisons for exo-atmospheric total solar irradiance measurements," Appl. Opt. 52, 7963-7980 (2013)
Exo-atmospheric solar irradiance measurements made by the solar irradiance community since 1978 have incorporated limiting apertures with diameters measured by a number of metrology laboratories using a variety of techniques. Knowledge of the aperture area is a critical component in the conversion of radiant flux measurements to solar irradiance. A National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) sponsored international comparison of aperture area measurements of limiting apertures provided by solar irradiance researchers was performed, the effort being executed by the National Institute of Standards and Technology (NIST) in coordination with the EOS Project Science Office. Apertures that had institutional heritage with historical solar irradiance measurements were measured using the absolute aperture measurement facility at NIST. The measurement technique employed noncontact video microscopy using high-accuracy translation stages. We have quantified the differences between the participating institutions’ aperture area measurements and find no evidence to support the hypothesis that preflight aperture area measurements were the root cause of discrepancies in long-term total solar irradiance satellite measurements. Another result is the assessment of uncertainties assigned to methods used by participants. We find that uncertainties assigned to a participant’s values may be underestimated.
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The acronyms are defined in Appendix A.
The TCTE and TSIS missions use the TIM instrument.
Table 2.
Apertures Submitted by the Institutions, with the Comparison Designation, the Institution and its Designation, the Material, Nominal Value of , and the Source and Date of the Submitted Aperture Values and Uncertainties
The NIST uncertainty components are given for , along with the combined standard uncertainty in mean radius and the expanded uncertainty in diameter at for the RMIB apertures 1S, 2S, 3S, 5S, and #10. The expanded uncertainties at in the measured aperture diameters for the previous measurements for the RMIB apertures are also given.
The NIST uncertainty components are given for , along with the combined standard uncertainty in mean radius and the expanded uncertainty in diameter at for the RMIB apertures #8, #5, #8.5, #3, and #9. The expanded uncertainties at in the measured aperture diameters for the previous measurements for the RMIB apertures are also given.
Table 5.
Uncertainty Components for the PMOD/WRC Aperturesa
Inst.
Unc.
PMOD609
PMOD611
SOVA R 111
SOVA R 113
VIRGO 2
VIRGO 3
NIST
103.9 nm
41.7 nm
54.7 nm
17.4 nm
42.8 nm
20.7 nm
NIST
13.0 nm
13.0 nm
13.0 nm
13.0 nm
13.0 nm
13.0 nm
NIST
4.0 nm
4.0 nm
4.0 nm
4.0 nm
4.0 nm
4.0 nm
NIST
7.9 nm
5.3 nm
5.3 nm
15.9 nm
2.6 nm
2.7 nm
NIST
60.4 nm
17.4 nm
9.3 nm
4.7 nm
5.6 nm
3.3 nm
NIST
,
121.3 nm
47.5 nm
57.4 nm
27.6 nm
45.3 nm
25.2 nm
NIST
,
0.485 μm
0.190 μm
0.230 μm
0.110 μm
0.181 μm
0.101 μm
PMOD/WRC
,
1.0 μm
1.0 μm
1.0 μm
1.0 μm
1.0 μm
1.0 μm
The NIST uncertainty components are given for , along with the combined standard uncertainty in mean radius and the expanded uncertainty in diameter at for the PMOD/WRC apertures. The expanded uncertainties at in the measured aperture diameters for the previous measurements for the PMOD/WRC apertures are also given.
The NIST uncertainty components are given for , along with the combined standard uncertainty in mean radius and the expanded uncertainty in diameter at for the LaRC apertures. The expanded uncertainties at in the measured aperture diameters for the previous measurements for the NASA LaRC apertures are also given.
The NIST uncertainty components are given for , along with the combined standard uncertainty in mean radius and the expanded uncertainty in diameter at for the JPL apertures. The expanded uncertainties at in the measured aperture diameters for the previous measurements for the NASA JPL apertures are also given.
Table 8.
Values for the Coefficient of Linear Expansion Used to Correct the NIST Measurement Results to 20°Ca
Comparison Designation
Participant Designation
Material
1, 2
1S, 2S
Ti
3, 4
3S, 5S
SST
5 to 10
#10, #8, #5, #8.5, #3, #9
SST
11 to 16
PMO609, PMO611, SOVA R 111, SOVA R 113, VIRGO 2, VIRGO 3
SST
17, 18, 19
A, C, D
Al
20
307NS
Cu
21 to 25
ACRII 1, ACRII 2, ACRIII 1, ACRIII 2, ACRIII 3
Al
Values for the aluminum and copper material were not provided by the participants, so typical values from a material database were used.
Table 9.
NIST Measurement Results of Apertures and the Results Submitted by the Institutionsa
Comp. Ap.
Inst.
Inst. Name
NIST
Inst.
1
RMIB
1S
78.7368
78.7545
1.00023
2
RMIB
2S
78.7534
78.7657
1.00016
3
RMIB
3S
79.3966
79.4193
1.00029
4
RMIB
5S
79.4422
79.4644
1.00028
5
RMIB
#10
78.4918
78.4966
1.00006
6
RMIB
#8
78.5037
78.4896
0.99982
7
RMIB
#5
19.7845
19.8010
1.00084
8
RMIB
#8.5
56.7972
56.8205
1.00041
9
RMIB
#3
78.3264
78.3734
1.00060
10
RMIB
#9
78.3605
78.4295
1.00088
11
PMOD/WRC
PMO609
19.5762
19.5910
1.00075
12
PMOD/WRC
PMO611
19.6546
19.6727
1.00092
13
PMOD/WRC
SOVA R 111
19.7030
19.7169
1.00071
14
PMOD/WRC
SOVA R 113
19.5808
19.5919
1.00056
15
PMOD/WRC
VIRGO 2
19.5771
19.5886
1.00059
16
PMOD/WRC
VIRGO 3
19.7567
19.7640
1.00037
17
LaRC
A
50.6085
50.5693
0.99923
18
LaRC
C
51.3070
51.2846
0.99956
19
LaRC
D
51.2521
51.1316
0.99765
20
LaRC
307NS
31.6356
31.7199
1.00267
21
JPL
ACRII 1
51.9351
51.6849
0.99518
22
JPL
ACRII 2
50.4882
50.2948
0.99617
23
JPL
ACRIII 1
49.8669
49.7287
0.99723
24
JPL
ACRIII 2
50.5308
50.3619
0.99666
25
JPL
ACRIII 3
49.8577
49.6641
0.99612
The expanded relative uncertainties in area, , and the expanded uncertainties in the ratio , are given at . The mean and standard deviation of the ratios by institution are RMIB, 1.00036 and 0.00034; PMOD/WRC, 1.00065 and 0.00020; LaRC, 0.99978 and 0.00021; and JPL, 0.99627 and 0.00076.
Tables (9)
Table 1.
Long-Term TSI Satellite Instruments and Associated Data Records from 1978 to the Present and Near Futurea
Instrument or Experiment/Platform
TSI Data Record
ERB, ERBE/Nimbus 7
Nov. 1978 to Dec. 1993
ACRIM I/SMM
Feb. 1980 to Jun. 1989
ERBE/ERBS
Oct. 1984 to Oct. 2005
ERBE/NOAA 9 Satellite
Jan. 1985 to Dec. 1989
ERBE/NOAA 10 Satellite
Oct. 1986 to Dec. 1987
ACRIM II/UARS
Oct. 1991 to Nov. 2001
SOVA/EURECA
Jul. 1992 to Jun. 1993
SOLCON/Spacelab 1, ATLAS and Hitchhiker (space shuttle)
Nov. 1983, Mar. 1992, Apr. 1993, Nov. 1994, Aug. 1997, Oct. 1998, Feb. 2003
The acronyms are defined in Appendix A.
The TCTE and TSIS missions use the TIM instrument.
Table 2.
Apertures Submitted by the Institutions, with the Comparison Designation, the Institution and its Designation, the Material, Nominal Value of , and the Source and Date of the Submitted Aperture Values and Uncertainties
The NIST uncertainty components are given for , along with the combined standard uncertainty in mean radius and the expanded uncertainty in diameter at for the RMIB apertures 1S, 2S, 3S, 5S, and #10. The expanded uncertainties at in the measured aperture diameters for the previous measurements for the RMIB apertures are also given.
The NIST uncertainty components are given for , along with the combined standard uncertainty in mean radius and the expanded uncertainty in diameter at for the RMIB apertures #8, #5, #8.5, #3, and #9. The expanded uncertainties at in the measured aperture diameters for the previous measurements for the RMIB apertures are also given.
Table 5.
Uncertainty Components for the PMOD/WRC Aperturesa
Inst.
Unc.
PMOD609
PMOD611
SOVA R 111
SOVA R 113
VIRGO 2
VIRGO 3
NIST
103.9 nm
41.7 nm
54.7 nm
17.4 nm
42.8 nm
20.7 nm
NIST
13.0 nm
13.0 nm
13.0 nm
13.0 nm
13.0 nm
13.0 nm
NIST
4.0 nm
4.0 nm
4.0 nm
4.0 nm
4.0 nm
4.0 nm
NIST
7.9 nm
5.3 nm
5.3 nm
15.9 nm
2.6 nm
2.7 nm
NIST
60.4 nm
17.4 nm
9.3 nm
4.7 nm
5.6 nm
3.3 nm
NIST
,
121.3 nm
47.5 nm
57.4 nm
27.6 nm
45.3 nm
25.2 nm
NIST
,
0.485 μm
0.190 μm
0.230 μm
0.110 μm
0.181 μm
0.101 μm
PMOD/WRC
,
1.0 μm
1.0 μm
1.0 μm
1.0 μm
1.0 μm
1.0 μm
The NIST uncertainty components are given for , along with the combined standard uncertainty in mean radius and the expanded uncertainty in diameter at for the PMOD/WRC apertures. The expanded uncertainties at in the measured aperture diameters for the previous measurements for the PMOD/WRC apertures are also given.
The NIST uncertainty components are given for , along with the combined standard uncertainty in mean radius and the expanded uncertainty in diameter at for the LaRC apertures. The expanded uncertainties at in the measured aperture diameters for the previous measurements for the NASA LaRC apertures are also given.
The NIST uncertainty components are given for , along with the combined standard uncertainty in mean radius and the expanded uncertainty in diameter at for the JPL apertures. The expanded uncertainties at in the measured aperture diameters for the previous measurements for the NASA JPL apertures are also given.
Table 8.
Values for the Coefficient of Linear Expansion Used to Correct the NIST Measurement Results to 20°Ca
Comparison Designation
Participant Designation
Material
1, 2
1S, 2S
Ti
3, 4
3S, 5S
SST
5 to 10
#10, #8, #5, #8.5, #3, #9
SST
11 to 16
PMO609, PMO611, SOVA R 111, SOVA R 113, VIRGO 2, VIRGO 3
SST
17, 18, 19
A, C, D
Al
20
307NS
Cu
21 to 25
ACRII 1, ACRII 2, ACRIII 1, ACRIII 2, ACRIII 3
Al
Values for the aluminum and copper material were not provided by the participants, so typical values from a material database were used.
Table 9.
NIST Measurement Results of Apertures and the Results Submitted by the Institutionsa
Comp. Ap.
Inst.
Inst. Name
NIST
Inst.
1
RMIB
1S
78.7368
78.7545
1.00023
2
RMIB
2S
78.7534
78.7657
1.00016
3
RMIB
3S
79.3966
79.4193
1.00029
4
RMIB
5S
79.4422
79.4644
1.00028
5
RMIB
#10
78.4918
78.4966
1.00006
6
RMIB
#8
78.5037
78.4896
0.99982
7
RMIB
#5
19.7845
19.8010
1.00084
8
RMIB
#8.5
56.7972
56.8205
1.00041
9
RMIB
#3
78.3264
78.3734
1.00060
10
RMIB
#9
78.3605
78.4295
1.00088
11
PMOD/WRC
PMO609
19.5762
19.5910
1.00075
12
PMOD/WRC
PMO611
19.6546
19.6727
1.00092
13
PMOD/WRC
SOVA R 111
19.7030
19.7169
1.00071
14
PMOD/WRC
SOVA R 113
19.5808
19.5919
1.00056
15
PMOD/WRC
VIRGO 2
19.5771
19.5886
1.00059
16
PMOD/WRC
VIRGO 3
19.7567
19.7640
1.00037
17
LaRC
A
50.6085
50.5693
0.99923
18
LaRC
C
51.3070
51.2846
0.99956
19
LaRC
D
51.2521
51.1316
0.99765
20
LaRC
307NS
31.6356
31.7199
1.00267
21
JPL
ACRII 1
51.9351
51.6849
0.99518
22
JPL
ACRII 2
50.4882
50.2948
0.99617
23
JPL
ACRIII 1
49.8669
49.7287
0.99723
24
JPL
ACRIII 2
50.5308
50.3619
0.99666
25
JPL
ACRIII 3
49.8577
49.6641
0.99612
The expanded relative uncertainties in area, , and the expanded uncertainties in the ratio , are given at . The mean and standard deviation of the ratios by institution are RMIB, 1.00036 and 0.00034; PMOD/WRC, 1.00065 and 0.00020; LaRC, 0.99978 and 0.00021; and JPL, 0.99627 and 0.00076.