I assume today's space probes transmit photographs in a digital format like jpeg. Before this, in what format did researchers receive photos taken by the various probes launched throughout the history of space exploration? Were they simply television-type transmissions?
2007-02-07 03:59:21 · 2 answers · asked by noedeparis 1 in Science & Mathematics ➔ Astronomy & Space
They were digital with few bits per data value and at a very slow bit rate. There was no significant compression. Analog TV was much too wide a bandwidth to send photo's. The signal to noise ratio wouldn't allow that wide a signal. Todays probes donot use something as crude as jpeg. One or two lunar probes that self destructed on the surface did use analog because of the short distance to the moon.
2007-02-07 04:05:52 · answer #1 · answered by Gene 7 · 0⤊ 0⤋
Space probes transmit raw images, not compressed images (at least not with a lossy compression method, like JPEG). Any compression used must be totally lossless. In other words the every pixel of the raw image must be pulled from the compressed data.
They transmit data using codes that actually ADD information to the bandwidth, called error-correction codes. This ensures the images and other data will arrive at earth, even if noise gets into the signal.
Space probes have used error-correction codes since the late 1950s, when it all started. Whatever type of video camera is used (vidicon, CCD, etc.) the data is always digitized, and framed for transmission, not framed for "TV". Re-framing the data for "TV" is done on the ground.
2007-02-07 05:29:12 · answer #2 · answered by tlbs101 7 · 1⤊ 0⤋