Local Mode Data

Introduction to Local Mode

If all nine MISR cameras were to transmit their data at full resolution, the data rate of the MISR instrument would be prohibitively high. For this reason, the typical MISR instrument operating mode commands 24 of its 36 channels into an averaging mode. This default mode is called Global Mode (GM). In this configuration all nadir (An) camera data are kept at the higher resolution, and all of the Red channels (Band 3) for the off-nadir cameras are kept at higher resolution (275 meters). The other channels are downsampled by one-quarter, to 1.1 kilometers. This downsampling is done by contiguous averaging of 4 crosstrack by 4 downtrack line samples, and is done electronically within the instrument before data transmission.

However, MISR can also be configured to disable this on-board data averaging and provide high resolution images in all 36 channels for selected targets and observation times. This capability is referred to as Local Mode (LM). The result is a scene with a crosstrack pixel spacing of 275 meters, with downtrack sampling also at 275 meters, over a spatial area of approximately 300 kilometers downtrack by about 400 kilometers crosstrack. Local Mode may be desired because the high-resolution data:

• Can facilitate comparisons with local, point observations acquired by field teams and aircraft;
• Allow better understanding of the anisotropy of a surface due to spatial variability (e.g. local topography, land cover type); and,
• Allow an independent validation of MISR's Global Mode data products.

MISR Local Mode data are available as geolocated calibrated radiances.

The MISR team maintains a list of targets for Local Mode data acquisitions. New targets may also be added to this database, but must occur well in advance of the data acquisitions. Targets are scheduled on a monthly basis based upon requests from the user community. However, one or two corrupt lines of data frequently occur in a Local Mode scene because of the high data rate, and no two Local Mode sites may be scheduled for a given orbit unless they are separated by 3000 kilometers in the downtrack direction. Before ordering Local Mode data, users should remember that all of the Red channels (Band 3), and all nadir imagery, are always acquired at the highest spatial resolution in the default Global Mode data product.

The Local Mode site database

The MISR Science Team and other users of MISR data have developed a database of Local Mode sites. This is available in PDF format, organized by site name or by site id. The MISR Local Mode Production Report is also available for determining processing status and history.

Special LM requests

Some MISR Local Mode sites are not collected routinely. These include sites used for image-based instrument calibration studies, those associated with intensive field campaigns, and those where only seasonal acquisitions are to be acquired. These requests are tabulated in the PDF files given below (files for future months become available approximately 2 weeks before the upcoming month).

Adding new sites

In order to schedule a Local Mode acquisition, a site must be on the currently released version of the Local Mode list. However, since the specific sites required by an investigator may change with time, it is possible to request additions or changes to the list. The requester of Local Mode data should be aware of the following schedule guidelines:

Two (2) months or more prior to a field campaign: Compile a list of field sites and dates where Local Mode data are to be requested. Submit these to the MISR Local Mode Science Coordinator (Ms. Barbara Gaitley) using the Ask MISR email form. Information should include, if known or appropriate, the following parameters. Database field sizes are indicated. Items marked with an asterisk (*) are required.

The Science Coordinator will determine if a site already exists within the Local Mode database. If the target is more than 50 kilometers away from an existing site, then a new site may be added. A mid-latitude target usually has three paths (that is, three opportunities) for viewing; targets at higher latitudes will have more than three opportunities. In rare instances, the decision to not add a site of a given location would reduce the number of available visits to two, in the mid-latitude example. This can be determined in advance, and the Coordinator will request justification from the requester before a final decision is made, should this be the case.

Six (6) weeks prior to the field campaign: The requester should review his experiment plan and sites for which Local Mode data are desired and verify that hte site exists on the MISR Local Mode list, as published on this web page, that the campaign dates are accurate, and that the site latitude and longitude are correct. He should notify the Coordinator of any necessary changes.

One (1) week prior to the month in which the campaign is conducted: Local Mode scheduling begins. All changes should be submitted prior to this deadline. If need be, the instrument command table may be re-written up to 24 hours before data acquisition, provided the target is in the Local Mode database. If this is not the case, last minute additions can be accommodated only by considering the campaign site a "target of opportunity". Manual scheduling would need approval from the MISR PI, and EOS Operations Center (EOC) manager. Notify the Science Coordinator should this be necessary.

Date versus path and orbit tables

These tables provide a listing of the path and orbit for a given date, beginning with launch and ending in 2008.