The potential for determining historic sea-ice extent from 1960´s Nimbus HRIR satellite data

A critical need in climate research is to obtain continuous high quality data records and images as far back in time as is practical. There is a wealth of early Earth-observing satellite data that were never fully explored due to the limitations of historical programs and processing systems. With the recent recovery of some of these data, there is now an opportunity to use this 1960s vintage data to create sea ice extent, climate data records (CDRs) for this era. The original engineers and researchers are now mostly in their late 70s and 80s, and contact with them is critical to answering some of the necessary instrumentation questions. Only a portion of the original 6-bit, 7 track tapes have been recovered and none has been converted to modern formats. If this work is not done now, we will have forever lost the opportunity. Satellites dedicated to polar visible or near infrared imaging for weather or climate purposes did not practically begin until the mid 1960´s. NASA began this effort with the Nimbus series of spacecraft. Nimbus I collected data during 1964. Nimbus II collected data from 1966-1969. Nimbus III collected data from 1969-1972. Data coverage was global with twice daily acquisitions. Unfortunately, the original downlink data was recorded on two inch Ampex tape media as an intermediate product and was never envisioned to be preserved in an archive. The original raw data contained all the detailed timings and calibration information needed to geo-rectify the data. NASA Goddard saved and is maintaining the higher-level products derived from the raw data, unfortunately without the timings and calibration. If even a few examples of these intermediate products could be found, it would help to improve the usefulness of the archive data product. The Nimbus HRIR (High Resolution Infrared Radiometer) Instrument data coverage is global, the reprocessing techniques could make new, 1960s-era data available to the entire Earth science community. The techniques we u- - se would bring the quality of archaic data from other Earth-observing satellites (not limited to Nimbus instruments) up to contemporary standards, reinvigorating the data sets for current applications. The objective of this project is to generate monthly (or better) seaice extent CDRs for the time intervals covered by NIMBUS I, II and III and TIROS 9 &10. This will require a multi-step process to define and build the CDRs. The initial step is the reprocessing and correcting of all the available HRIR data. The available MRIR (medium band) data will be examined to see whether they would help. AVCS visible band video images and TIROS visible images (film) will be acquired to help in the analysis. Next techniques must be developed to determine the monthly average sea-ice extent from these data. We expect clouds will be the most difficult challenge in the process. With data records provided on multiple orbits on a daily basis, our preliminary research confirms that we can separate clouds from ice by animating the data in Google Earth. Finally, the standards for these 1960s CDRs must be published along with the resultant data.