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Nimbus Image Dissector Camera System Visible Imagery L1, HDF5

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 System (IDCS) onboard the Nimbus 3 satellite.

Table of Contents

  1. Contacts and Acknowledgments
  2. Detailed Data Description
  3. Data Access and Tools
  4. Data Acquisition and Processing
  5. References and Related Publications
  6. Document Information

Citing These Data

The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.

Gallaher, David and G. Garrett Campbell. 2013. Nimbus Image Dissector Camera System Visible Imagery L1, HDF5, [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center. doi:10.5067/NIMBUS/NmIDCS1H.

Overview

Platform

Nimbus 3 Satellite

Sensor

Image Dissector Camera System (IDCS)

Spatial Coverage

Global

Spatial Resolution

Roughly 2 km

Temporal Coverage

23 April, 1969 to 21 January, 1970 (intermittent)

Temporal Resolution

200 seconds

Parameters

Visible Brightness

Data Format

HDF5

Metadata Access

View Metadata Record

Data Access

See the Order Data page for a list of options.

1. Contacts and Acknowledgments

Investigators

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

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

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, and NSIDC student workers William Harris and Amy Randall.

2. Detailed Data Description

This data set consists of black-and-white Image Dissector Camera System (IDCS) images that were acquired by the Nimbus 3 satellite between 23 April, 1969 and 21 January, 1970. NSIDC researchers and staff scanned the images from archival rolls of 70 mm, black-and-white film. Each HDF5-formatted data file contains an array of 8-bit gray scale values, estimates of the latitude and longitude for each pixel, and a gray scale calibration map. Browse images are also available.

File Naming Convention

This section explains the file naming convention used for NmIDCS1H data files.

Example file name:
NmIDCS1H.[OOOO].YYYY.[MM].[DD].[HH].[MI].[SS].[DDD].[Tx.Ty].[Tn].Q[n].[varies].crc.hdf

Refer to Table 2 for descriptions of the file name variables listed above.

Where:

Table 2. File Naming Convention Variables and Descriptions
Variable Description
OOOO Orbit number
YYYY Year (1969 or 1970)
MM Month
DD Day
HH Hour
MI Minute
SS Second
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.

File Size

Data files typically range between 7 MB - 10 MB.

Spatial Coverage

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.

Spatial Resolution

Roughly 2 km.

Projection and Grid Description

Estimated latitude and longitude is provided for each pixel.

Temporal Coverage

Intermittent images are available from 23 April, 1969 to 21 January, 1970. The Granules by Day page lists the number of granules that were produced for each day of the data record.

Temporal Resolution

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.

Parameter or Variable

Table 5 describes the data fields and corresponding attributes stored in NmIDCS1H data files.

Table 5. NmIDCS1H Data Fields
Data Field Description Attributes Value
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)
units 1
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
units degrees_north
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
units degrees_east
raw_brightness Raw 8-bit gray scale values

3. Data Access and Tools

Data Access

Please visit the Order Data page to see options for obtaining NmIDCS1H data files.

Software and Tools

HDF-compatible software packages, such as HDFView and Panoply, can be used to read, extract, and display NmIDCS1H data files.

4. Data Acquisition and Processing

Data Acquisition Methods

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.

Derivation Techniques and Algorithms

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.

Processing Steps

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 PIs constructed individual histograms from all images in an orbit and matched histograms between many orbits.

Quality Assessment

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.

Error Sources

Navigation

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.

Image Quality

The PIs estimate that the actual gray scale resolution is 4-bit, limited by the initial sensitivity of the IDCS and the accumulated degradation due to 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. Nevertherless, the IDCS represents a considerable improvement compared with the earlier AVCS instrument.

Sensor or Instrument Description

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.

5. References and Related Publications

References

Gallaher, D., G. G. Campbell, and W. N. Meier. In Press. Anomalous Variability in Antarctic Sea Ice Extents During the 1960s with the Use of Nimbus Satellite Data. Journal of Selected Topics in Applied Earth Observations and Remote Sensing.

Meier, W. N., D. Gallaher, and G. G. Campbell. 2013. New Estimates of Arctic and Antarctic Sea Ice Extent During September 1964 from Recovered Nimbus I Satellite Imagery. The Cryosphere Discuss 7:35-53. doi: 10.5194/tcd-7-35-2013.

Related Web Sites

6. Document Information

Acronyms and Abbreviations

The acronyms and abbreviations used in this document are listed in Table 7.

Table 7. Acronyms and Abbreviations
Acronym Description
DAAC Distributed Active Archive Center
ESDT Earth Science Data Type
GSFC Goddard Space Flight Center
HDF Hierarchical Data Format
IDCS Image Dissector Camera System
NASA The National Aeronautics and Space Administration
NOAA The National Oceanic and Atmospheric Administration
NSIDC The National Snow and Ice Data Center

Document Creation Date

July 2013

Document URL

http://nsidc.org/data/docs/daac/nimbus/nmidcs1h/index.html