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21-561: It operated in daytime-only operations from 2011 to 2023 due to battery malfunction, requiring sunlight to power the radar. On December 20, 2023, the Cloud Profiling Radar was deactivated for the final time, ending the data collection portion of the mission. The mission was selected under NASA's Earth System Science Pathfinder program in 1999. Ball Aerospace & Technologies Corp. in Boulder, Colorado , designed and built

42-475: A telescope pointed at or near CloudSat whenever the satellite was above the horizon (which could be of order one hour per day at a typical location). The narrow-band, Doppler-shifted radar signal would probably have been detectable in even fairly short integrations no matter where a radio telescope were pointed, whenever CloudSat was above the horizon. Ball Aerospace %26 Technologies Corp. Ball Aerospace & Technologies Corp. , commonly Ball Aerospace ,

63-770: The Canadian Space Agency . The overall design of the CPR was simple, well understood, and had a strong heritage from the many cloud radars already in operation in ground-based and airborne applications. Most design parameters and subsystem configurations were nearly identical to those for the Airborne Cloud Radar, which has been flying on the NASA DC-8 aircraft since 1998. The CPR capitalized on existing radar expertise and experience at JPL. Other radars already flown successfully or developed by JPL include

84-816: The Seasat SAR, the Shuttle Imaging Radars (SIR-A, SIR-B, SIR-C), the Shuttle Radar Topography Mission (SRTM), Magellan Venus Radar Mapper, Cassini Radar (mapping Saturn's moon Titan), NSCAT, and SeaWinds . Based on radar lifetime data, NASA expected the radar to operate for at least three years with a 99% probability. CloudSat is managed by the Jet Propulsion Laboratory. Colorado State University provides scientific leadership and science data processing and distribution. The cost of this project

105-440: The point spread function for adjacent stars, other nearby satellites, point-source light pollution from large cities on Earth, ...). There are roughly 57 bright navigational stars in common use. However, for more complex missions, entire star field databases are used to determine spacecraft orientation. A typical star catalogue for high-fidelity attitude determination is originated from a standard base catalog (for example from

126-529: The spacecraft . CloudSat's primary mission was scheduled to continue for 22 months to allow more than one seasonal cycle to be observed. The main instrument on CloudSat was the Cloud Profiling Radar (CPR), a 94-GHz nadir-looking radar that measures the power backscattered by clouds as a function of distance from the radar. The radar instrument was developed at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, with hardware contributions from

147-445: The 1950s through the 1980s, although some systems use it to this day. Many models are currently available. There also exist open projects designed to be used for the global CubeSat researchers' and developers' community. Star trackers, which require high sensitivity, may become confused by sunlight reflected from the spacecraft, or by exhaust gas plumes from the spacecraft thrusters (either sunlight reflection or contamination of

168-452: The Earth's rotation, stars that are in a usable location change over the course of a day and the location of the target. Generally, a selection of several bright stars would be used and one would be selected at launch time. For guidance systems based solely on star tracking, some sort of recording mechanism, typically a magnetic tape , was pre-recorded with a signal that represented the angle of

189-461: The INS. The rest of the system works as before; the signal from the INS roughly positions the star tracker, which then measures the actual location of the star and produces an error signal. This signal is then used to correct the position being generated from the INS, reducing the accumulated drift back to the limit of the accuracy of the tracker. These "stellar inertial" systems were especially common from

210-538: The N-1 navigation system developed for the SM-64 Navaho cruise missile drifted at a rate of 1 nautical mile per hour, meaning that after a two-hour flight the INS would be indicating a position 2 nautical miles (3.7 km; 2.3 mi) away from its actual location. This was outside the desired accuracy of about half a mile. In the case of an INS, the magnetic tape can be removed and those signals instead provided by

231-654: The aerospace industry include lubricants, optical systems, star trackers and antennas. As a wholly-owned subsidiary of the Ball Corporation, Ball Aerospace was cited in 2023 as the 54th largest defense contractor in the world. Both parent and subsidiary headquarters are co-located in Broomfield, Colorado. In August 2023, Ball Corporation agreed to divest Ball Aerospace to BAE Systems Inc. for $ 5.6 billion in cash. On February 14, 2024 The companies announced that all regulatory approvals were in place to allow

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252-402: The deal to complete. The deal was closed on February 16, 2024. Star tracker A star tracker is an optical device that measures the positions of stars using photocells or a camera. As the positions of many stars have been measured by astronomers to a high degree of accuracy, a star tracker on a satellite or spacecraft may be used to determine the orientation (or attitude ) of

273-453: The known pattern of stars in the sky. In the 1950s and early 1960s, star trackers were an important part of early long-range ballistic missiles and cruise missiles , in the era when inertial navigation systems (INS) were not sufficiently accurate for intercontinental ranges. Consider a Cold War missile flying towards its target; it initially starts by flying northward, passes over the arctic, and then begins flying southward again. From

294-436: The missile's perspective, stars behind it appear to move closer to the southern horizon while those in front are rising. Before flight, one can calculate the relative angle of a star based on where the missile should be at that instant if it is in the correct location. That can then be compared to the measured location to produce an "error off" signal that can be used to bring the missile back onto its correct trajectory. Due to

315-528: The photocell, producing a signal that was then smoothed to produce an alternating current output. The phase of that signal was compared to the one on the tape to produce a guidance signal. Star trackers were often combined with an INS. INS systems measure accelerations and integrate those over time to determine a velocity and, optionally, double-integrate to produce a location relative to its launch location. Even tiny measurement errors, when integrated, add up to an appreciable error known as "drift". For instance,

336-406: The spacecraft with respect to the stars. In order to do this, the star tracker must obtain an image of the stars, measure their apparent position in the reference frame of the spacecraft, and identify the stars so their position can be compared with their known absolute position from a star catalog. A star tracker may include a processor to identify stars by comparing the pattern of observed stars with

357-436: The star over the period of a day. At launch, the tape was forwarded to the appropriate time. During the flight, the signal on the tape was used to roughly position a telescope so it would point at the expected position of the star. At the telescope's focus was a photocell and some sort of signal-generator, typically a spinning disk known as a chopper . The chopper causes the image of the star to repeatedly appear and disappear on

378-409: The star tracker window). Star trackers are also susceptible to a variety of errors (low spatial frequency, high spatial frequency, temporal, ...) in addition to a variety of optical sources of error ( spherical aberration , chromatic aberration , etc.). There are also many potential sources of confusion for the star identification algorithm ( planets , comets , supernovae , the bimodal character of

399-742: Was acquired by BAE Systems Inc. in 2024, and is operated as a new division within BAE called Space & Mission systems. Ball Aerospace began building pointing controls for military rockets in 1956. The aerospace part of the Ball Corporation was then known as Ball Brothers Research Corporation , and later won a contract to build some of NASA 's first spacecraft, the Orbiting Solar Observatory satellites. The company has been responsible for numerous technological and scientific projects and continues to provide aerospace technology to NASA and related industries. Other products and services for

420-592: Was an American manufacturer of spacecraft, components and instruments for national defense, civil space and commercial space applications. Until 2024, the firm was a wholly owned subsidiary of Ball Corporation , with primary offices in Boulder, Colorado , and facilities in Broomfield and Westminster in Colorado , with smaller offices in New Mexico , Ohio , northern Virginia , Missouri and Maryland . It

441-498: Was approximately $ 200 million. Power levels of the CloudSat radar were such that the receiver electronics deployed on a typical radio telescope could be burned out if the telescope was pointing at the zenith during an overflight. Moreover, the typical receiver would probably saturate during an overflight (or near overflight) no matter where the radio telescope were pointed, and similarly strong signal levels would have been received if

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