Figure 2.1: The ATS-
Figure 2.5: A WINDCO terminal, developed between 1971-
Analogue signals were digitised so that different levels of brightness were assigned numerical values and these values were stored on tape. According to this NASA document, one ATS image could use an entire tape reel when digitised (4 reels for colour). Ultimately, seven track 18 inch reels were used, and these could store 70 images (roughly a day and a half's worth of data). It took an estimated 4 hours between image transmission from the satellite to being visible on a terminal on the ground.
2. Satellite Meteorology
By the late 1960s, the use of satellites to look at the weather was increasingly common, but the technology itself was still in its infancy, and even by the end of the Apollo era there were still many experiments designed to see if the data from satellites were as reliable as those from traditional ground and atmospheric measurements.
Early satellites were launched with a lifespan of just a few months, and the images were examined on their return to Earth. These included the early Soviet Kosmos satellites as well as American efforts. Advances in communication techniques then allowed signals from an orbiting satellite to be sent back to a receiving station on Earth where they could be translated into photographic images. Although primitive by 2010's standards, the absence of modern circuit board, micro-
There are two basic type of satellite orbit discussed in this work: geostationary and geosynchronous. Geostationary satellites are placed in a position above the Earth that allows them to observe the same features on the ground at all times. Geosynchronous satellites orbit in such a way that they pass over the same place on the ground at the same time each day. They are effectively always following the same path, but the rotation of the earth underneath them means that each time the return to a specific point in their orbit, they are over a different part of the planet.
Images from a number of different types of satellite are examined in this research: ATS, ESSA (and its ITOS and NOAA variations) and NIMBUS.
2.1 ATS Satellites
ATS stands for Application Technology Satellite, and the satellite used in this research is predominantly the ATS-
The camera used to image the earth was developed by Dr Verner Suomi of the University of Wisconsin-
Figure 2.2 – The ATS-
While in orbit it span at around 120 rpm, and with each spin it scanned a small line of the Earth's surface, each line representing 3.2 km of latitude. On the next spin it scanned a slightly lower latitude, and over 2400 revolutions it would achieve full coverage. It would take roughly 20 minutes to compose an entire image, after which the camera would reset itself and the process would start again. Most of the archives show a single image for each day, but in reality there was a very good record. As will be in seen in a later chapter this can be used to pinpoint the timing of Apollo images very precisely.
The colour image comprised a blue, green and red channel. These three channels worked for just 3 months, after which the red and blue channels ceased to function. Black & white images were still produced until the mid-
The satellite became the first to photograph the full Earth from space in high quality colour (see figure 2.3), and this led to the first colour time lapse film of the Earth from space (see below).
Figure 2.3: Earth from space, November 1967 (Example source)
The first US sourced high quality full Earth black and white images (and the first satellite images to feature Earth and moon together, although arguably this distinction belongs to Lunar Orbiter 1) were done by ATS-
The image shown above in figure 2.3 has often been mis-
Interestingly, the satellite does have a direct link with Apollo.
This NASA page reports that it provided television relay for the live Apollo 11 TV broadcasts to Radio Television Caracas, a Venezuelan broadcaster. It is important to note that it served purely as a relay for the TV signal. It took approximately half an hour for the satellites own camera to create a single image and reset itself, it did not have the capacity to broadcast its own images live. It would also not have been possible for Apollo 11 to send a signal direct to the satellite as it would not have been visible. The main TV signal for Apollo 11's moon walk (Extra-
Figure 2.4: VHF antennae used to receive ATS-
This document describes early techniques where each strip would be printed, with characters such as '*','/' and ')' in order used to simulate a grey scale, involving a huge amount of paper. Kinescope assemblies (A technique for recording TV images directly on still or moving film) were also used to photograph the TV images.
Information could be recorded on tape and analysed later, but the systems were bulky and slow (figure 2.5).