There are two types of communication systems: radio frequency (RF) and free space optical (FSO), FSO is also referred to as laser communications (lasercom). The three functions of a communications system are receiving commands from Earth (uplink), transmitting data down to Earth (downlink) and transmitting or receiving information from another satellite (crosslink or inter-satellite link) (figure 9.1). A communications system consists of the ground segment: one or more ground stations located on Earth, and the space segment: one or more spacecraft and their respective communication payloads. For most missions the communication system enables the spacecraft to transmit data and telemetry to Earth, receive commands from Earth, and relay information from one spacecraft to another. The communication system is an essential part of a spacecraft. (WFF) Wallops Flight Facility 9.1 Introduction (SCaN) Space Communications and Navigation (SBIR) Small Business Innovative Research (PAT) Pointing, Acquisition, and Tracking (OSIRIS) Optical Space Infrared Downlink System (OCTL) Optical Communication Telescope Laboratory (OCSD) Optical Communication and Sensor Demonstration (NTIA) National Telecommunications and Information Administration (NOAA) National Oceanic and Atmospheric Administration (NICT) National Institute of Information and Communications Technology (LLCD) Lunar Laser Communications Demonstration (LADEE) Lunar Atmosphere and Dust Environment Explorer (JAXA) Japanese Aerospace Exploration Agency (ISOC) Inter-spacecraft Optical Communicator (ISM) Industrial, Scientific, and Medical (ISARA) Integrated Solar Array and Reflectarray Antenna (IEEE) Institute of Electrical and Electronics Engineers (FIPS) Federal Information Processing Standard (DVB-S2) Digital Video Broadcast Satellite Second Generation (DORA) Deployable Optical Receiver Aperture (ADCS) Attitude Determination and Control System 9.2.3 Major Components in Smallsat Communication Systems.Use of radio signals for interior sensing is planned for continued use in the coming years. NASA has long worked to find ways to mitigate risk of a more significant collision, such as through the development of other technologies that have successfully redirected small asteroids. The release explains that asteroids hit the earth every year, though most are so small that they simply burn up. The release says that at one time the asteroid was thought to be a threat to Earth - though predictions have evolved and the threat was disproven. Apophis is nearly four football fields across, with a diameter of around 1,100 feet. That asteroid, named Apophis, is predicted to pass within 20,000 miles of Earth, thousands of miles closer than geostationary satellites and around 200,000 miles closer to Earth than the moon. Tuesday’s test of the system follows tests earlier this year conducted at the moon, and is itself only preparation for a repeat of the process on a much larger asteroid that will pass by Earth in April of 2029. The resulting signal will be recovered in New Mexico and California and interpreted to learn more about the makeup of the body. That signal will travel farther than the distance to the moon to reach the asteroid. The HAARP will transmit a signal around 9.6 megahertz at two-second intervals. NASA has a long history of detecting and mapping asteroids using telescopes and radar, but using longer wavelength signals to map the insides is a new development. This will allow the scientists to learn the distribution of mass, information useful for defending against an asteroid impact. The purpose of the experiment is to probe the interior of the asteroid, NASA investigator Mark Haynes explained in a news release from UAS.
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