The Level-1A product is a simple concatenation of Level-0 data with a Header, which could easily be reversed back to Level-0. Level-1A remains in a binary format and is not in HDF. The Level-1B format groups like data together.
The Visible and Infrared Scanner (VIRS) sensor is one of the five instruments on the TRMM satellite. The VIRS instrument has a swath width of 720 km and a horizontal resolution of 2 km at nadir. VIRS is similar to the Advanced Very High Resolution Radiometer (AVHRR) now in operation on polar-orbital environmental satellites.
The TRMM Visible and Infrared Scanner (VIRS) Level 1B Calibrated Radiance Product (1B01) contains calibrated radiances and auxiliary geolocation information from the five channels of the VIRS instrument, for each pixel of each scan. The data are stored in the Hierarchical Data Format (HDF), which includes both core and product specific metadata applicable to the VIRS measurements. A file contains a single orbit of data with a file size of about 95 MB. The EOSDIS "swath" structure is used to accommodate the actual geophysical data arrays.