The Nimbus Image Dissector Camera System Visible Imagery L1, HDF5 (NmIDCS1H) data set consists of black-and-white images captured by the Image Dissector Camera Systems (IDCSs) onboard the Nimbus 3 and Nimbus 4 satellites. Data are provided as HDF5-formatted files. Browse images are also available.
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Nimbus Image Dissector Camera System Visible Imagery L1, HDF5, Version 1
|Temporal Resolution:||210 second|
|Data Contributor(s):||David Gallaher, G. Garrett Campbell|
|Metadata XML:||View Metadata Record|
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 Image Dissector Camera System Visible Imagery L1, HDF5, 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/NmIDCS1H. [Date Accessed].
Detailed Data Description
NSIDC researchers and staff scanned black-and-white Image Dissector Camera System (IDCS) images that were acquired by the Nimbus 3 and Nimbus 4 satellites between 23 April, 1969 and 08 April, 1971 from archival rolls of 70 mm, black-and-white film. Each data file contains an array of 8-bit gray scale values, plus estimates of the latitude and longitude for each pixel and a gray scale calibration map. Browse images are also available.
Data are provided as HDF5-formatted files. HDF-EOS (Hierarchical Data Format - Earth Observing System) is a self-describing file format based on HDF that was developed specifically for distributing and archiving data collected by NASA EOS satellites. For more information, visit the HDF-EOS Tools and Information Center. Browse images are also available.
This section explains the file naming convention used for NmIDCS1H data files.
Example file name:
Refer to Table 1 for descriptions of the file name variables listed above.
|YYYY||Year (1969 or 1970)|
|DDD||Day of year|
|[Tx.Ty]||Tx = image center, x-direction, from fiducial mark|
|Ty = image center, y-direction, from fiducial mark|
|Tn||Frame number on film reel|
|Q[n]||Quality (Q1 = failed; Q2 = passed)|
|Varies||Internal use. May not be present.|
Data files typically range between 7 MB - 10 MB.
Coverage is global, however some regions (parts of Alaska, for example) are not available due to technological limitations at the time of the mission. Individual images cover approximately 2000 km x 2000 km.
Roughly 2 km.
Estimated latitude and longitude is provided for each pixel.
Intermittent coverage is available from 23 April, 1969 to 08 April, 1971. The Granules by Day page lists the number of granules that were recovered for each of the period of record.
Successive images are separated in time by 210 seconds. Note that due to the IDCS's rotating scan system successive images overlap each other in space by 50 percent. Refer to the Data Acquisition Methods section of this document for details.
Table 2 describes the data fields and corresponding attributes stored in NmIDCS1H data files.
|brightness||Calibrated 8-bit gray scale values (see gray scale Calibration below)||DOI||10.5067/NIMBUS/NmIDCS1H|
|ESDT||NmIDCS1H (data set short name)|
|long_ESDT||Nimbus Image Dissector Camera System Visible Imagery L1, HDF5 (data set long name)|
|byte cosine sun zenith angle||Estimated sun zenith angles (cosine)||–||–|
|byte cosine view angle||Estimating view angles (cosine)||–||–|
|latitude||Estimated latitudes||nav_info||standard navigation|
|long scan line time since 1970||Image acquisition date and time in seconds since 00:00:00, 01 January 1970||–||–|
|longitude||Estimated longitudes||nav_info||standard navigation|
|raw_brightness||Raw 8-bit gray scale values||–||–|
Software and Tools
Data Acquisition and Processing
To obtain the along-track scan, the IDCS rotated the sensor counter to the motion of the satellite for 200 seconds (the cross-track scan was acquired by a drift tube sensor). After 200 seconds, the sensor returned to the starting position to began the next acquisition 210 seconds after the previous image. As a result, successive images overlap each other in space by 50 percent.
The IDCS output was stored as brightness levels on a tape recorder and transmitted as an analog signal to ground stations within range of the satellite and eventually to Goddard Space Flight Center (GSFC). At GSFC, the images were reconstructed on a television picture tube and captured on black-and-white 70 mm film. The film images were then duplicated onto long reels and archived at NASA (and later NOAA). The film rolls remained in storage for some 40 years until NSIDC investigators undertook the task of digitizing the images for new climate research and preservation.
Trajectory and Attitude Data
Navigation parameters were derived from the user guide description of the instrument. Satellite ephemeris and image times were used to estimate the cosine of the sun zenith angle and viewing angle and latitude and longitude for every pixel. Although the images contained tick marks indicating lines of latitude and longitude, the investigators believe the calculated positions better align the images with identifiable landmarks.
The PIs received the IDCS images on 300-foot rolls of 70 mm, black-and-white film comprising many days of data. NSIDC researchers and staff scanned the film images, including margins, to 8-bit TIFF files. The 8-bit scanning depth exceeds the true gray scale resolution. The images were also oversampled in space to ensure a strong correlation between adjacent pixels.
The digitized images were first trimmed and then evaluated with specially written software that allowed an operator to identify the center point from fiducial marks and read the image time. Latitudes and longitudes were then estimated for every pixel based on satellite ephemeris and image acquisition time. Intermediate files were inspected visually and flagged for quality, and then final images were written to HDF5-formatted files.
Gray Scale Calibration
To reduce differences in brightness between images due to variations in film developing, the investigators constructed individual histograms from all images in an orbit and matched histograms between many orbits.
None of the original Nimbus calibration programs have survived. Furthermore, the navigation accuracy is limited by the satellite attitude control, which was no better than 1 degree, and no further information about the attitude is available. By eye, the navigation and continental boundaries line up with some random error.
However, due to ambiguity in the user guide description of the instrument, the navigation has systemic errors that produce noticeable mismatches between images showing the same geographic features. This error may have arisen because the roll, pitch, and yaw of the satellite were not recorded. Based on a review of many images of the Mediterranean, navigation accuracy is better in equatorial regions.
The investigators estimate that the effective gray scale resolution is 4-bit, a result of the initial sensitivity of the IDCS degraded by accumulated photo processing and digitization. However, the resolution is sufficient to at least qualitatively recognize clouds, ocean, land, and ice. Albedos and optical depths are likely irretrievable.
These data should be considered semi-quantitative. Features such as ocean and land areas and weather and sea ice variations are typically distinguishable. Subtle changes in the land surface, however, have been lost due to variations in photographic processing and should be treated with caution. For example, although these data can reveal historical storm tracks and sea ice boundaries, they would not be suitable for radiation budget studies.
The Image Dissector Camera System (IDCS) was a shutterless, electronic scan and step tube mounted behind a 108 degree wide-angle, 5.7 mm focal length lens. The camera was installed on the bottom of the satellite sensory ring and pointed vertically down toward the earth at all times. The optical field of view was 73.6 degree in the direction of flight and 98.2 degree in the plane perpendicular to flight. The instrument optics focused the image on the dissector tube's photosensitive surface, while a line-scanning beam scanned the surface at 4 Hz with a frame period of 200 seconds. At the nominal spacecraft altitude of 1100 km, the resulting pictures covered approximately 1400 km on a side with a ground resolution of 3 km at nadir. Scanning and stepping functions occurred continuously as the satellite progressed along its orbital path. Pictures were either transmitted to ground stations in real time or stored on magnetic tape for subsequent transmission.
For additional information about the Nimbus IDCS, see the National Space Science Data Center's Image Dissector Camera System (IDCS) Web page.
|V1.1 (11 December 2014)||
Nimbus-4 data added.
|V1 (11 July 2013)||Initial release.|
References and Related Publications
Contacts and Acknowledgments
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
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, and NSIDC student workers William Harris and Amy Randall.
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