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Data Set ID:
NmHRIR3G

Nimbus High Resolution Infrared Radiometer Remapped Digital Data Daily L3, GeoTIFF, Version 1

This data set (NmHRIR3G) consists of daily composites constructed from Nimbus 1, Nimbus 2, and Nimbus 3 satellites High Resolution Infrared Radiometer (HRIR) data for the region between 60 N and 60 S. Measurements were obtained during 1964, 1966, and 1969. Data are available as GeoTIFFs and browse images. For the HDF5 formatted version of these data, see the Nimbus High Resolution Infrared Radiometer Remapped Digital Data Daily L3, HDF5 data set.

Geographic Coverage

Spatial Coverage:
  • N: 60, S: -60, E: 180, W: -180

Spatial Resolution:
  • 20 km x 20 km
Temporal Coverage:
  • 29 August 1964 to 21 September 1964
  • 16 May 1966 to 14 November 1966
  • 17 April 1969 to 30 November 1969
Temporal Resolution: 1 day
Parameter(s):
  • Infrared Wavelengths > Brightness Temperature
Platform(s) NIMBUS-1, NIMBUS-2, NIMBUS-3
Sensor(s): HRIR
Data Format(s):
  • GeoTIFF
Version: V1
Data Contributor(s): David Gallaher, G. Garrett Campbell

Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Gallaher, D. and G. Campbell. 2013. Nimbus High Resolution Infrared Radiometer Remapped Digital Data Daily L3, GeoTIFF, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/NIMBUS/NmHRIR3G. [Date Accessed].

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Detailed Data Description

Format

Data files are available in Geographic Tagged Image File Format (GeoTIFF).

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File Naming Convention

This section explains the file naming convention used for NmHRIR3G data files.

Example file name:
NmHRIR3H.downIR.[YYYY][MM][DD].G.tif

Refer to Table 1 for descriptions of the file name variables listed above.

Table 1. NmHRIR3G File Naming Convention
Variable Description
NmHRIR3G Product
DownIR To remove reflected light contamination in the raw data, only the descending half of the orbit was used.
YYYY Year
MM Month
DD Day
G Equatorial projection
.tif GeoTIFF
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File Size

Data files are roughly 16 MB.

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Spatial Coverage

Northernmost Latitude: 60° N
Southernmost Latitude: 60° S
Easternmost Longitude: 180° E
Westernmost Longitude: 180° W

Spatial Resolution

Roughly 20 km

Projection and Grid Description

Data are provided in a 20 km cylindrical equidistant projection. The grid was constructed by defining a 2000 east-west by 664 north-south global array at the equator to establish roughly 20 km x 20 km cells. Only the portion of the grid from 60° N to 60° S (2000 X 664) is saved for the final output.

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Temporal Coverage

Intermittent data are available within the following date ranges:

Satellite Date Range
Table 2: Temporal Coverage by Satellite
Nimbus 1 29 August to 21 September, 1964
Nimbus 2 16 May to 14 November, 1966
Nimbus 3 17 April, 1969 to 30 November, 1969

 

Temporal Resolution

Daily

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Parameter or Variable

The parameter of interest in this data set is brightness temperature. See the Data Acquisition and Processing section of this document for details.

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Software and Tools

Any GeoTIFF-compatible software package can be used to read and display NmHRIR3G data files.

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Data Acquisition and Processing

Data Acquisition Methods

The HRIR on the Nimbus I, II, and III satellites transformed measured radiation into electrical voltages that were recorded on tape and played back when the satellite came within range of a receiving station. These data were then transmitted to the Goddard Space Flight Center (GSFC), where they were calibrated, converted to temperatures, and archived on 7-track, digital magnetic tapes. In 2009, the contents of these tapes were recovered and written to a binary tape emulation file format (TAP) for preservation. GES DISC, the NASA Goddard Earth Sciences Data and Information Services Center, archives and distributes these data and maintains historical Nimbus documentation such as instrument user guides and mission reports.

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Derivation Techniques and Algorithms

Processing Steps

To construct the daily composites, all reprocessed HRIR swaths for each 24-hour period were accumulated from the Nimbus High Resolution Infrared Radiometer Digital Swath Data Level 1 (NmHRIR1H) data set. When multiple observations were available in a grid cell, the observation closest to satellite nadir was selected. The cosine of the selected observation's view angle is stored in the view angle for brightness temperature data field for users who wish to make additional corrections based on view angle.

The underlying NmHRIR1H data have been corrected to minimize seemingly random alignment errors that caused cloud edges and land features to appear jagged. See Processing Steps in the NmHRIR1H documentation for details.

Error Sources

Most extant Nimbus 1 and 2 observations were collected at night, however a few daytime orbits have survived. Although the daytime measurements are contaminated by reflected solar radiation, these data have been included for their qualitative and historical value.

Whereas Nimbus I and II operated almost exclusively in nighttime mode, Nimbus III was equipped with an infrared filter that could be inserted into the optical path to acquire daytime reflected solar radiation. However, no flag was set in the data to indicate whether the filter was in or out. Furthermore, a few daytime orbits were collected with no filter in place and contain mixed IR and visible radiation.

In general, daytime orbits appear to correspond to temperatures below 150 K. Bit 7 in the Flags data field is set to on to indicate the PIs' best guess that the filter was in place. Although no calibration exists for the daytime visible data, obvious distinctions between land, cloud, water, and ice surfaces are apparent. However, the visible observations are so scattered in time and space that constructing land surface or cloud maps from these data alone would result in significant sampling errors.

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Quality Assessment

The correction applied in the NmHRIR1H data set improves the visual appearance of the data and better represents the shapes of clouds and coastlines. In regions with very little spatial information, for example where the measurements are very noisy or very uniform, the shifts offer little or no improvement.

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Sensor or Instrument Description

The HRIR on Nimbus I and II was a single scanning radiometer that operated in the 3.4 µm to 4.2 µm near-infrared region. The instrument utilized an optical system and a lead selenide photoconductive detector cell to obtain measurements of blackbody temperatures from 210K – 330K. To allow daytime operation, the Nimbus III HRIR was augmented with a band-pass filter that transmitted reflected solar radiation in the 0.7 µm to 1.3 µm region. The change-over from nighttime to daytime operation was accomplished by actuating a relay, either automatically or by ground station command, to insert the filter into the optical path.

For all three missions, the scan mirror was inclined to 45 degrees with a scan rate of 44.7 revolutions per minute. The instantaneous field of view was 8.8 milliradians and the scan line separation was 8.3 km. The radiometer's instantaneous field of view covered roughly 0.5 degrees, which at an altitude of 1100 km corresponded to a ground resolution of approximately 8 km at nadir.

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References and Related Publications

Contacts and Acknowledgments

nvestigators

David Gallaher
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA

G. Garrett Campbell
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA

Acknowledgements: 

The Nimbus Data Rescue Project: Nimbus 1, 2, 3 was supported by NASA contract #NNG08HZ07C as a subtask to NSIDC at the University of Colorado. The PIs also wish to thank Alex Calder, Carl Gallaher, and Anna Schroeder for their contributions to this project.

Document Information

DOCUMENT CREATION DATE

October 2013

No technical references available for this data set.
No FAQs or How Tos available for this data set.

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Email: nsidc@nsidc.org