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channels 17 and 18. Channels 17 and 18 are located in a spectral region (0.94mm) sensitive to atmospheric water vapor, a quantity that affects the accurate calibration of AVHRR Ch. 2. Using the Ch17 to Ch 18 ratio, an accurate guess at the total precipitable water (TPW) is obtained to further increase the accuracy of MODIS to AVHRR SNO calibrations. The Libyan Desert and Dome-C calibration sites are used when MODIS/AVHRR SNOs do not occur. Here, the AVHRR to MODIS ratio of reflectances is modeled as a third-order polynomial using the natural logarithm of TWP from the NCEP reanalysis. Using these two methods, monthly calibration slopes are generated with a linear fit forced through the origin of the adjusted MODIS reflectances versus AVHRR counts.
241:
Mexico, USA , an absolute calibration for NOAA-9 was transferred from a well calibrated spectrometer on board a U-2 aircraft flying at an altitude of ~18 km in a congruent path with the NOAA-9 satellite above. After being corrected for the relative degradation, the absolute calibration of NOAA-9 is then passed onto NOAA −7 and −11 via a linear relationship using Libyan Desert observations that are restricted to similar viewing geometries as well as dates in the same calendar month , and any sensor degradation is corrected for by adjusting the slope (as a function of days after launch) between the albedo and digital count signal recorded .
24:
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absolutely calibrate AVHRRs via simultaneous nadir overpasses (SNOs) of both MODIS/AVHRR and AVHRR/AVHRR satellite pairs as well as MODIS-characterized surface reflectances for a Libyan Desert target and Dome-C in
Antarctica . Ultimately, each individual calibration event available (MODIS/AVHRR SNO, Dome C, Libyan Desert, or AVHRR/AVHRR SNO) is used to provide a calibration slope time series for a given AVHRR sensor. Heidinger et al. use a second-order polynomial from a least-squares fit to determine the time series.
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commonly used for land studies, while data from both satellites are used for atmosphere and ocean studies. Together they provide twice-daily global coverage, and ensure that data for any region of the earth are no more than six hours old. The swath width, the width of the area on the Earth's surface that the satellite can "see", is approximately 2,500 kilometers (~1,540 mi). The satellites orbit between 833 or 870 kilometers (+/− 19 kilometers, 516–541 miles) above the surface of the Earth.
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observations over the ocean, an initial minimum guess to the calibration slope is made. An iterative method is then used to achieve the optimal slope values for Ch. 1 with slope corrections adjusting for uncertainties in ocean reflectance, water vapor, ozone, and noise. Ch. 2 is then subsequently calibrated under the condition that the stratus cloud optical thickness in both channels must be the same (spectrally uniform in the visible) if their calibrations are correct .
275:. Vermote and Saleous present a methodology that uses MODIS to characterize the BRDF of an invariant desert site. Due to differences in the spectral bands used for the instruments' channels, spectral translation equations were derived to accurately transfer the calibration accounting for these differences. Finally, the ratio of AVHRR observed to that modeled from the MODIS observation is used to determine the sensor degradation and adjust the calibration accordingly.
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transfer the accurate calibration of one AVHRRs reflectances to the counts of an un-calibrated AVHRR and produce appropriate calibration slopes. These AVHRR/AVHRR SNOs do not provide an absolute calibration point themselves; rather they act as anchors for the relative calibration between AVHRRs that can be used to transfer the ultimate MODIS calibration.
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In another similar method using surface targets, Loeb uses spatiotemporal uniform ice surfaces in
Greenland and Antarctica to produce second-order polynomial reflectance calibration curves as a function of solar zenith angle; calibrated NOAA-9 near-nadir reflectances are used to generate the curves
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To extend the MODIS reference back for AVHRRs prior to the MODIS era (pre-2000), Heidinger et al. use the stable Earth targets of Dome C in
Antarctica and the Libyan Desert. MODIS mean nadir reflectances over the target are determined and are plotted versus the solar zenith angle. The counts for
166:
because of the comparatively long records of data already accumulated (over 20 years). The main difficulty associated with these investigations is to properly deal with the many limitations of these instruments, especially in the early period (sensor calibration, orbital drift, limited spectral and
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Long-term record continuity is achieved by the normalization between two sensors. First, observations from the operational time period overlap of two sensors are processed. Next, the two global SURFACE maps are compared via a scatter plot. Additionally, observations are corrected for changes in
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After filtering, the global maps are segregated into monthly mean SURFACE, two bi-weekly SURFACE, and a mean TOTAL reflectance maps. The monthly mean SURFACE reflectance maps are used to detect long-term trends in calibration. The bi-weekly SURFACE maps are compared to each other and are used to
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Rao and Chen use the Libyan Desert as a radiometrically stable calibration target to derive relative annual degradation rates for
Channels 1 and 2 for AVHRR sensors on board the NOAA -7, -9, and -11 satellites. Additionally, with an aircraft field campaign over the White Sands desert site in New
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meteorological satellites in orbit at all times, with one satellite crossing the equator in the early morning and early evening and the other crossing the equator in the afternoon and late evening. The primary sensor on board both satellites is the AVHRR instrument. Morning-satellite data are most
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method begins with the detection of clouds and corrections for ozone, Rayleigh scatter, and seasonal variations in irradiance to produce surface reflectances. Monthly histograms of surface reflectance are then produced for various surface types, and various histogram limits are then applied as a
226:
One major design constraint of AVHRR instruments is that they lack the capability to perform accurate, onboard calibrations once on orbit . Thus, post-launch on-orbit calibration activities (known as vicarious calibration methods) must be performed to update and ensure the accuracy of retrieved
222:
where S and I are the slope and intercept (respectively) of the calibration regression . However, the highly accurate prelaunch calibration will degrade during launch and transit to orbit as well as during the operational life of the instrument . Halthore et al. note that sensor degradation is
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that will convert observed MODIS scenes into those that a perfectly calibrated AVHRR would see. For MODIS/AVHRR SNO occurrences, it was determined that the ratio of AVHRR to MODIS radiances in both Ch1 and Ch2 are modeled well by a second-order polynomial of the radio of MODIS reflectances in
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One final method used by
Heidinger et al. for extending the MODIS calibration back to AVHRRs that operated outside of the MODIS era is through direct AVHRR/AVHRR SNOs. Here, the counts from AVHRRs are plotted and a regression forced through the origin calculated. This regression is used to
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sensor onboard NASA's TERRA and AQUA satellites. The MODIS instrument has high calibration accuracy and can track its own radiometric changes due to the inclusion of an onboard calibration system for the VIS/NIR spectral region . The following method utilizes the high accuracy of MODIS to
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In the discussion thus far, methods have been posed that can calibrate individual or are limited to a few AVHRR sensors. However, one major challenge from a climate point of view is the need for record continuity spanning 30+ years of three generations of AVHRR instruments as well as more
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It was found that the ratio of calibration coefficients derived by Loeb and Rao and Chen are independent of solar zenith angle, thus implying that the NOAA-9-derived calibration curves provide an accurate relation between the solar zenith angle and observed reflectance over
Greenland and
262:
Iwabuchi employed a method to calibrate NOAA-11 and -14 that uses clear-sky ocean and stratus cloud reflectance observations in a region of the NW Pacific Ocean and radiative transfer calculations of a theoretical molecular atmosphere to calibrate AVHRR Ch. 1. Using a month of clear-sky
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applications of the AVHRR sensor are based on validation (matchup) techniques of co-located ground observations and satellite observations. Alternatively, radiative transfer calculations are performed. There are specialized codes which allow simulation of the AVHRR observable
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solar zenith angle caused by orbital drift. Ultimately, a line is fit to determine the overall long-term drift in calibration, and, after a sensor is corrected for drift, normalization is performed on observations that occur during the same operational period .
952:
Rao, C.R.N. and J. Chen. 1995. Inter-satellite calibration linkages for the visible and near-infrared channels of the
Advanced Very High Resolution Radiometer on the NOAA-7, −9, and −11 spacecraft. International Journal of Remote Sensing. Vol. 16.
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AVHRR observations at a given solar zenith angle and corresponding MODIS reflectance, corrected for TWP, are then used to determine what AVHRR value would be provided it had the MODIS calibration. The calibration slope is now calculated.
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Rao, C.R.N. and J. Chen. 1999. Revised post-launch calibration of the visible and near-infrared channels of the
Advanced Very High Resolution Radiometer on the NOAA-14 spacecraft. International Journal of Remote Sensing. Vol. 20.
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Finally, the TOTAL maps are used to detect and assess bias in the processing methodology. The target histograms are also examined, as changes in mode reflectances and in population are likely the result of changes in calibration.
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Iwabuchi, H. 2003. Calibration of the visible and near-infrared channels of NOAA-11 and NOAA-14 AVHRRs by using reflections from molecular atmosphere and stratus cloud. International
Journal of Remote Sensing. Vol. 24.
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radiances and the subsequent products derived from these values . Numerous studies have been performed to update the calibration coefficients and provide more accurate retrievals versus using the pre-launch calibration.
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of the Earth. These sensors have proven useful for a number of other applications, however, including the surveillance of land surfaces, ocean state, aerosols, etc. AVHRR data are particularly relevant to study
921:
Heidinger, A. K. et al. 2002. Using
Moderate Resolution Imaging Spectrometer (MODIS) to calibrate Advanced Very High Resolution Radiometer reflectance channels. Journal of Geophysical Research. Vol. 107.
96:(AVHRR) instrument is a space-borne sensor that measures the reflectance of the Earth in five spectral bands that are relatively wide by today's standards. AVHRR instruments are or have been carried by the
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Smith, G.R. et al. 1988. Calibration of the Solar Channels of the NOAA-9 AVHRR Using High Altitude Aircraft Measurements. Journal of Atmospheric and Oceanic Technology. Vol. 5. pp. 631–639.
296:. Several artifacts may exist in the nominal AVHRR calibration, and even in updated calibrations, that cause a discontinuity in the long-term radiance record constructed from multiple satellites .
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Heidinger, A.K. et al. 2010. Deriving an inter-sensor consistent calibration for the AVHRR solar reflectance data record. International Journal of Remote Sensing. Vol. 31. pp. 6493–6517.
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Cao, C. et al. 2008. Assessing the consistency of AVHRR and MODIS L1B reflectance for generating Fundamental Climate Data Records. Journal of Geophysical Research. Vol. 113. D09114.
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mainly caused by thermal cycling, outgassing in the filters, damage from higher energy radiation (such as ultraviolet (UV)), and condensation of outgassed gases onto sensitive surfaces.
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Brest and Rossow , and the updated methodology , put forth a robust method for calibration monitoring of individual sensors and normalization of all sensors to a common standard. The
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Loeb, N.G. 1997. In-flight calibration of NOAA AVHRR visible and near-IR bands over Greenland and Antarctica. International Journal of Remote Sensing. Vol. 18. pp. 477–490.
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Xiong, X. et al. 2010. On-Orbit Calibration and Performance of Aqua MODIS Reflective Solar Bands. IEEE Transactions on Geoscience and Remote Sensing. Vol 48. pp. 535–546.
112:(0.9 micrometres) regions, a third one is located around 3.5 micrometres, and another two the thermal radiation emitted by the planet, around 11 and 12 micrometres.
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Molling, C.C. et al. 2010. Calibrations for AVHRR channels 1 and 2: review and path towards consensus. International Journal of Remote Sensing. Vol. 31. pp. 6519–6540.
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Prior to launch, the visible channels (Ch. 1 and 2) of AVHRR sensors are calibrated by the instrument manufacturer, ITT, Aerospace/Communications Division, and are traceable to
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Brest, C.L. and W.B. Rossow. 1992. Radiometric calibration and monitoring of NOAA AVHRR data for ISCCP. International Journal of Remote Sensing. Vol. 13. pp. 235–273.
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standards. The calibration relationship between electronic digital count response (C) of the sensor and the albedo (A) of the calibration target are linearly regressed:
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Vermote, E.F. and N.Z. Saleous. 2006. Calibration of NOAA16 AVHRR over a desert site using MODIS data. Remote Sensing of Environment. Vol. 105. pp. 214–220.
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Halthore, R. et al. 2008. Role of Aerosol Absorption in Satellite Sensor Calibration. IEEE Geoscience and Remote Sensing Letters. Vol. 5. pp. 157–161.
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Brest, C.L. et al. 1997. Update of Radiance Calibrations for ISCCP. Journal of Atmospheric and Oceanic Technology. Vol 14. pp. 1091–1109.
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Frey, C.; Kuenzer, C.; Dech, S. (2012). "Quantitative comparison of the operational NOAA AVHRR LST product of DLR and the MODIS LST product V005".
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119:. The last version, AVHRR/3, first carried on NOAA-15 launched in May 1998, acquires data in six channels. The AVHRR has been succeeded by the
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The highest ground resolution that can be obtained from the current AVHRR instruments is 1.1-kilometer (0.68 mi) per pixel at the
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MCST. MODIS Level 1B Algorithm Theoretical Basis Document, Version 3. Goddard Space Flight Center. Greenbelt, MD. December 2005.
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Metop-B takes over prime operational service: Long-term continuity of vital weather and climate data ensured from polar orbit
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filter to the original sensor observations and ultimately aggregated to produce a global, cloud free surface reflectance.
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A more contemporary calibration method for AVHRR uses the on-orbit calibration capabilities of the VIS/IR channels of
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satellites. The instrument scans several channels; two are centered on the red (0.6 micrometres) and near-
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Methods for extending the calibration and record continuity also make use of similar calibration activities .
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NOAA KLM User's Guide with NOAA-N, -N' Supplement. NOAA NESDIS NCDC. Asheville, NC. February 2009.
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Another recent method for the absolute calibration of the AHVRR record makes use of the contemporary
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that can then derive the calibrations for other AHVRRs in orbit (e.g. NOAA-11, -12, and -14).
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Data from AVHRR (in its three evolutions) has been collected continuously since 1981.
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sensor onboard NASA's Terra and Aqua led to the development of AVHRR's follow-on,
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The primary purpose of these instruments is to monitor clouds and to measure the
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TIROS/NOAA dates from USGS website and from NOAA POES Status website
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Calibration using the moderate-resolution imaging spectroradiometer
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International Satellite Cloud Climatology Project (ISCCP) method
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satellites are part of the EUMETSAT Polar System (EPS) run by
696:. 11th International Conference on Clouds and Precipitation.
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International Satellite Cloud Climatology Project (ISCCP)
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Pre-launch calibration of visible channels (Ch. 1 and 2)
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USGS Earth Resources Observation and Science AVHRR page
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EUMETSAT announcement of operational data dissemination
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satellites with AVHRR instruments will be succeeded by
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and radiances in near infrared and infrared channels.
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On-orbit individual/few sensor absolute calibration
694:On the Retrieval and Analysis of Multilevel Clouds
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395:satellites with a European MetImage instrument.
1033:National Oceanic and Atmospheric Administration
98:National Oceanic and Atmospheric Administration
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115:The first AVHRR instrument was a four-channel
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376:. VIIRS is currently operating on board the
692:Baum, Bryan A.; Wielicki, Bruce A. (1992).
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287:Long-term calibration and record continuity
100:(NOAA) family of polar orbiting platforms (
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313:detect short-term changes in calibration.
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355:Calibration using direct AVHRR/AVHRR SNOs
121:Visible Infrared Imaging Radiometer Suite
68:Learn how and when to remove this message
998:Advanced Very High Resolution Radiometer
989:Advanced Very High Resolution Radiometer
726:Official NOAA POES satellite users guide
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94:Advanced Very-High-Resolution Radiometer
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31:This article includes a list of general
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170:The AVHRR instrument also flies on the
88:acquired from the NOAA/ AVHRR satellite
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174:series of satellites. The three
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164:environmental degradation
399:Launch and service dates
344:radiative transfer model
86:sea surface temperatures
808:4 December 2008 at the
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200:brightness temperatures
52:more precise citations.
1038:Spacecraft instruments
770:NASA Suomi NPP Website
364:Next-generation system
135:NOAA has at least two
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1043:Satellite meteorology
724:NOAA KLM User's Guide
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928:10.1029/2001JD002035
913:10.1029/2007JD009363
384:satellites. Whereas
957:pp. 3485–3491.
953:pp. 1931–1942.
937:pp. 5367–5378.
879:2012IJRS...33.7165F
267:Vermote and Saleous
84:An image of global
837:9 May 2009 at the
760:NASA MODIS Website
758:NASA MODIS Website
635:17 September 2012
568:21 September 2000
565:21 September 2000
515:13 September 1994
509:24 September 1988
501:17 September 1991
495:17 September 1986
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873:(22): 7165–7183.
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673:Ocean temperature
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551:13 May 1998
543:23 May 2007
526:14 May 1991
523:13 May 1991
487:11 May 1994
459:7 June 1986
421:
415:Service end
409:Launch date
367:
358:
349:
341:
333:
324:
315:
311:
303:
290:
282:
270:
261:
254:Antarctica.
252:
248:
239:
236:Rao and Chen
225:
221:
209:
193:
169:
152:
149:
142:
134:
127:spacecraft.
114:
93:
91:
64:
55:
36:
15:
470:3 May 1983
50:introducing
1027:Categories
679:References
117:radiometer
33:references
895:128981116
420:TIROS-N
378:Suomi NPP
131:Operation
835:Archived
806:Archived
667:See also
655:present
646:Metop-C
641:present
632:Metop-B
618:Metop-A
613:present
604:NOAA-19
599:present
590:NOAA-18
576:NOAA-17
562:NOAA-16
557:present
548:NOAA-15
534:NOAA-14
520:NOAA-12
506:NOAA-11
492:NOAA-10
393:MetOp-SG
386:EUMETSAT
258:Iwabuchi
184:MetOp-SG
180:EUMETSAT
110:infrared
58:May 2020
875:Bibcode
478:NOAA-9
464:NOAA-8
450:NOAA-7
436:NOAA-6
382:NOAA-20
46:improve
893:
279:Others
35:, but
891:S2CID
736:RTTOV
389:MetOp
374:VIIRS
370:MODIS
336:MODIS
294:VIIRS
273:MODIS
176:MetOp
172:MetOp
145:nadir
106:MetOp
1018:NASA
1010:NASA
1002:USGS
993:NOAA
380:and
245:Loeb
212:NIST
162:and
102:POES
92:The
1016:at
1008:at
1000:at
991:at
982:at
924:doi
909:doi
883:doi
702:hdl
1029::
889:.
881:.
871:33
869:.
714:^
186:.
147:.
930:.
926::
915:.
911::
897:.
885::
877::
708:.
704::
71:)
65:(
60:)
56:(
42:.
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