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The inverse or time-reversed process of absorption is thermal radiation. Much of the thermal energy in matter consists of random motion of charged particles, and this energy can be radiated away from the matter. The resulting radiation may subsequently be absorbed by another piece of matter, with the deposited energy heating the material. [55]
The Consultative Committee for Space Data Systems packet telemetry standard defines the protocol used for the transmission of spacecraft instrument data over the deep-space channel. Under this standard, an image or other data sent from a spacecraft instrument is transmitted using one or more packets.
A packet is a block of data with length that can vary between successive packets, ranging from 7 to 65,542 bytes, including the packet header. Packetized data is transmitted via frames, which are fixed-length data blocks. The size of a frame, including frame header and control information, can range up to 2048 bytes.
With this form of staggered PRF, a packet of pulses is transmitted with a fixed interval between each pulse, and then another packet is transmitted with a slightly different interval. Target reflections appear at different ranges for each packet ; these differences are accumulated and then simple arithmetical techniques may be applied to ...
In outer space, the communication range of free-space optical communication is currently of the order of hundreds of thousands of kilometers. [1] Laser-based optical communication has been demonstrated between the Earth and Moon and it has the potential to bridge interplanetary distances of millions of kilometers, using optical telescopes as ...
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. [1]: 26‑1 As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. [2]
Any signal of a limited width in time or space requires many frequency components around a center frequency within a bandwidth inversely proportional to that width; even a gaussian function is considered a wave packet because its Fourier transform is a "packet" of waves of frequencies clustered around a central frequency. [2]
NASA's Vision Mission for the Innovative Interstellar Explorer considered using optical-laser communication, as did the 1980s era TAU probe. It has also been proposed that higher frequency signals, such as lasers operating at visible light frequencies, may prove to be a fruitful method of interstellar communication; at a given frequency it takes surprisingly small energy output for a laser ...