A new series in this generation began with the launch of TIROS-N on October 13, 1978. This was the first to carry the AVHRR (described on p.14-2), along with the first sounder, TOVS (TIROS Operational Vertical Sounder) designed to profile temperature and water vapor. TOVS is actually a three instrument complex: HIRS-2 (High Resolution IR Sounder), with 20 channels; SSU (Stratospheric Sounding Unit), with 3 channels near 15 µm, and the MSU (Microwave Sounding Unit), a passive scanning microwave spectrometer with 4 channels in the 5.5 µm interval. These instruments are the mainstays of the subsequent NOAA-6 (launched on June 27, 1979) through NOAA-14 (December 30, 1994) metsats; the SBUV is also part of NOAA-9 and NOAA-11. Even-numbered NOAA metsats have North to South equatorial crossing times near 7:30 A.M. and have orbit repeat periods (re-occupy approximately the same paths) of 4 to 5 days; the odd-numbered ones cross N-S at night (2:30 A.M.) and have 8-9 day repeat periods.

Here is a NOAA-9 AVHRR image in the visible of Hurricane Gloria as it neared the East Coast on September 27, 1997:

A NOAA-6 IR image, in which lighter tones are color-enhanced to bring out details, of Super Typhoon Angela in the western Pacific shows its status on November 11, 1995:

Like most multi-channel systems, different AVHRR bands can be combined into color composites, as demonstrated by this rendition of Hurricane Fran on September 4, 1996:

The Soviet Union/CIS has sent up more than 25 polar-orbiting metsats in its three Meteor Series, starting in March of 1969 and continuing through 1994. Other metsats were included in their Kosmos series.

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