Thought we were done talking about clouds from space? Nope!

Since the beginning of the space age, people have thought of work for satellites to do that other systems could not. One of these tasks was weather forecasting, particularly predicting cloud cover for military purposes. The Television Infrared Observation Satellite Program, or TIROS program, was initially a classified military reconnaissance program under the United States Air Force, but it was transferred to NASA in mid-1959 because weather observation was considered appropriate for a civilian agency and not the military. Also, the military didn’t want a weather satellite but don’t worry, they would get one later.

The TIROS program includes the original TIROS-1 through 10; the TIROS Operational System, which had nine satellites designated ESSA-1 through ESSA-9; the Improved TIROS, which had nine satellites with various designations, including NOAA-1; TIROS-N with five satellites; and Advanced TIROS-N, which started with NOAA-8 in 1983 and continues to this day. The most recent satellite in this group is NOAA-19, which was launched in 2009 and is still operational. In fact, we’re going to tell you about NOAA-19 in an upcoming episode of Daily Space.

The first Television Infrared Observation Satellite, TIROS-1, was launched a year after NASA took over in April 1960. It was a simple cylindrical satellite with two cameras on the bottom, one fixed antenna on the top to send and receive science data, and two fixed antennas on the bottom to downlink telemetry. Like other satellites of the time, TIROS-1 was solar-powered. It worked – mostly – and proved that satellites could be used for Earth observation.

The cameras on TIROS-1 produced black and white images – sufficient for the primary mission of photographing clouds – using television video tubes. These tubes worked sort of like modern digital camera sensors, interpreting brightness by the intensity of an electrical signal and then building up an image by scanning lines left to right, bottom to top. The cameras had a ground resolution of 30 meters per pixel with a swath width of 300 kilometers. This resolution was useful for determining large storm patterns from cloud cover but could also capture phenomena as small as individual tornadoes.

TIROS-1 also introduced different satellite orientation sensors – Sun and horizon sensors – updated versions of which are now widely used on virtually all satellites.

TIROS-5, part of the original series of ten satellites, was launched on June 19, 1962, on a Thor-Delta rocket. This satellite was launched into a higher inclination orbit than the four predecessors, allowing TIROS-5 to see more of the Earth. The satellite was a roughly one-meter diameter, spin-stabilized cylinder, allowing the cameras to sweep around and cover a much larger area in each orbit than if it was pointed straight down, effectively getting 65 degrees of inclination coverage from its 58-degree inclination orbit.

This spin was controlled by small solid motors that used a primitive but effective magnetic torque to control attitude relative to the ground, allowing ground controllers to identify where images were taken within two degrees of accuracy. Previous TIROS satellites had wobbled due to the Earth’s magnetic field, meaning scientists couldn’t tell precisely where the cameras were pointed. That’s not very useful for a weather satellite.

TIROS-5’s medium-angle camera failed seventeen days after launch, but the spacecraft itself remained functioning until May 14, 1963, when the wide-angle camera failed. Most of the camera was still working, but the electronics for the critical shutter mechanism had failed. After this failure, TIROS-5 was turned off and left to decay from orbit.

Fortunately, TIROS-6 was launched in September 1962, before TIROS-5 completely failed, and was launched into a similar orbit.

As of early-June 2022, eight of the first ten TIROS satellites, including TIROS-5, are still in orbit.

More Information

Dark clouds: The secret meteorological satellite program (part 1) (The Space Review)

Dark clouds: The secret meteorological satellite program (part 2) (The Space Review)

TIROS-5 mission page (NASA)

TIROS mission page (NASA)