The STAR-2 Bus is a fully redundant, flight-proven, spacecraft bus designed for geosynchronous missions.
25-483: It is a satellite platform , designed and developed by Thomas van der Heyden for the Indonesian Cakrawarta satellite program in the early 1990s, now manufactured by Northrop Grumman Innovation Systems with an apogee kick motor to place a communications satellite into geostationary orbit , a thruster to provide the satellite with orbital station-keeping for a 15-year mission, and solar arrays to provide
50-567: A domino effect known as Kessler syndrome . NASA's Orbital Debris Program tracks over 25,000 objects larger than 10 cm diameter in LEO, while the estimated number between 1 and 10 cm is 500,000, and the number of particles bigger than 1 mm exceeds 100 million. The particles travel at speeds up to 7.8 km/s (28,000 km/h; 17,500 mph), so even a small impact can severely damage a spacecraft. [REDACTED] This article incorporates public domain material from websites or documents of
75-595: A satellite or spacecraft , in which the payload and all scientific instruments are held. Bus-derived satellites are less customized than specially-produced satellites, but have specific equipment added to meet customer requirements , for example with specialized sensors or transponders , in order to achieve a specific mission. They are commonly used for geosynchronous satellites, particularly communications satellites , but are most commonly used in spacecraft which occupy low Earth orbit missions. Some satellite bus examples include: A bus typically consists of
100-534: A satellite into a LEO, and a satellite there needs less powerful amplifiers for successful transmission, LEO is used for many communication applications, such as the Iridium phone system . Some communication satellites use much higher geostationary orbits and move at the same angular velocity as the Earth as to appear stationary above one location on the planet. Unlike geosynchronous satellites , satellites in low orbit have
125-441: A small field of view and can only observe and communicate with a fraction of the Earth at a given time. This means that a large network (or constellation ) of satellites is required to provide continuous coverage. Satellites at lower altitudes of orbit are in the atmosphere and suffer from rapid orbital decay , requiring either periodic re-boosting to maintain stable orbits, or the launching of replacements for those that re-enter
150-433: A subset of LEO. These orbits, with low orbital inclination , allow rapid revisit times over low-latitude locations on Earth. Prograde equatorial LEOs also have lower delta-v launch requirements because they take advantage of the Earth's rotation. Other useful LEO orbits including polar orbits and Sun-synchronous orbits have a higher inclinations to the equator and provide coverage for higher latitudes on Earth. Some of
175-430: Is a modular, mass efficient structure, designed for simplified integration to reduce manufacturing cycle times. The structure is supported by a composite thrust cylinder, to which the bus, payload, nadir and base panels are connected. Energy from two multi-panel solar wings and lithium-ion batteries is electronically processed to provide 36 volts regulated power to the satellite throughout the mission. All active units aboard
200-496: Is only slightly less than on the Earth's surface. This is because the distance to LEO from the Earth's surface is much less than the Earth's radius. However, an object in orbit is in a permanent free fall around Earth, because in orbit the gravitational force and the centrifugal force balance each other out. As a result, spacecraft in orbit continue to stay in orbit, and people inside or outside such craft continuously experience weightlessness . Objects in LEO orbit Earth between
225-568: The National Security Agency (NSA). Due to the size and mass envelope of the satellite, the GEOStar-2 bus is compatible with almost all commercially available launch vehicles, maximizing opportunity for launch and access to space. While dedicated or single launch services are more readily available, the GEOStar-2 bus targets shared launch opportunities, where launch cost and launch-sharing opportunities are favorable. Customers can purchase
250-402: The radius of Earth and near the beginning of the inner Van Allen radiation belt . The term LEO region is used for the area of space below an altitude of 2,000 km (1,200 mi) (about one-third of Earth's radius). Objects in orbits that pass through this zone, even if they have an apogee further out or are sub-orbital , are carefully tracked since they present a collision risk to
275-414: The GEOStar-2 bus can be adapted for MSS, Earth and space science applications, as well as for technology demonstration or risk reduction programs. Depending on mission duration requirements, the GEOStar-2 bus can accommodate payloads in excess of 500 kilograms, and provide up to 5550 watts of power. Instrument data can be provided in standard format such as CCSDS or through secured encryption, as approved by
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#1732883629410300-411: The GEOStar-2 bus spacecraft bus alone, or as part of a turn-key service that includes an integrated payload, network operations center and launch vehicle. NGIS conducts spacecraft commissioning from its own ground station prior to transferring spacecraft control to the customer's operations center. Satellite bus A satellite bus (or spacecraft bus ) is the main body and structural component of
325-498: The LEO region but are not in a LEO orbit because they re-enter the atmosphere . The distinction between LEO orbits and the LEO region is especially important for analysis of possible collisions between objects which may not themselves be in LEO but could collide with satellites or debris in LEO orbits. The mean orbital velocity needed to maintain a stable low Earth orbit is about 7.8 km/s (4.8 mi/s), which translates to 28,000 km/h (17,000 mph). However, this depends on
350-541: The altitude above ground can vary by as much as 30 km (19 mi) (especially for polar orbits ) due to the oblateness of Earth's spheroid figure and local topography . While definitions based on altitude are inherently ambiguous, most of them fall within the range specified by an orbit period of 128 minutes because, according to Kepler's third law , this corresponds to a semi-major axis of 8,413 km (5,228 mi). For circular orbits, this in turn corresponds to an altitude of 2,042 km (1,269 mi) above
375-433: The atmosphere. The effects of adding such quantities of vaporized metals to Earth's stratosphere are potentially of concern but currently unknown. The LEO environment is becoming congested with space debris because of the frequency of object launches. This has caused growing concern in recent years, since collisions at orbital velocities can be dangerous or deadly. Collisions can produce additional space debris, creating
400-455: The denser part of the atmosphere and below the inner Van Allen radiation belt . They encounter atmospheric drag from gases in the thermosphere (approximately 80–600 km above the surface) or exosphere (approximately 600 km or 400 mi and higher), depending on orbit height. Satellites in orbits that reach altitudes below 300 km (190 mi) decay quickly due to atmospheric drag. Equatorial low Earth orbits ( ELEO ) are
425-403: The exact altitude of the orbit. Calculated for a circular orbit of 200 km (120 mi) the orbital velocity is 7.79 km/s (4.84 mi/s), but for a higher 1,500 km (930 mi) orbit the velocity is reduced to 7.12 km/s (4.42 mi/s). The launch vehicle's delta-v needed to achieve low Earth orbit starts around 9.4 km/s (5.8 mi/s). The pull of gravity in LEO
450-647: The first generation of Starlink satellites used polar orbits which provide coverage everywhere on Earth. Later Starlink constellations orbit at a lower inclination and provide more coverage for populated areas. Higher orbits include medium Earth orbit (MEO), sometimes called intermediate circular orbit (ICO), and further above, geostationary orbit (GEO). Orbits higher than low orbit can lead to early failure of electronic components due to intense radiation and charge accumulation. In 2017, " very low Earth orbits " ( VLEO ) began to be seen in regulatory filings. These orbits, below about 450 km (280 mi), require
475-472: The following subsystems: Low Earth orbit A low Earth orbit ( LEO ) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, peaking in number at an altitude around 800 km (500 mi), while the farthest in LEO, before medium Earth orbit (MEO), have an altitude of 2,000 kilometers, about one-third of
500-472: The many LEO satellites. No human spaceflights other than the lunar missions of the Apollo program (1968-1972) and the 2024 Polaris Dawn have taken place beyond LEO. All space stations to date have operated geocentric within LEO. A wide variety of sources define LEO in terms of altitude . The altitude of an object in an elliptic orbit can vary significantly along the orbit. Even for circular orbits ,
525-455: The mean radius of Earth, which is consistent with some of the upper altitude limits in some LEO definitions. The LEO region is defined by some sources as a region in space that LEO orbits occupy. Some highly elliptical orbits may pass through the LEO region near their lowest altitude (or perigee ) but are not in a LEO orbit because their highest altitude (or apogee ) exceeds 2,000 km (1,243 mi). Sub-orbital objects can also reach
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#1732883629410550-402: The satellite are connected through a 1553 data bus. Commands and telemetry are processed through the flight software resident on the flight processor, which provides robust autonomous control to all GEOStar-2 satellites. The modularity of the structure and the standard 1553 interfaces allow parallel assembly and test of the bus and payload systems, reducing manufacturing schedule risk by minimizing
575-443: The satellite payload with 5 kW of electrical power. NGIS's GEOStar-2 bus design is unique within the satellite industry. NGIS's GEOStar-2 bus provides an affordable low-to-medium power satellite platform that is ideal for missions of this size. Rather than being a less efficient version of a larger, heavier product, NGIS's GEOStar-2 bus is designed specifically for the 1000 to 5550 watts payload class. The GEOStar-2 bus satellite
600-640: The time spent in serial satellite integration and test flow. GEOStar-2 is designed for missions up to 15 years in duration. The propulsion system is sized for ten years of station keeping in geosynchronous orbit. Built-in radiation hardness for the severe geosynchronous environment is achieved through conservative selection of electronic parts. Several available options augment the basic bus to provide improved pointing, more payload power, secure communications, higher downlink data rates or enhanced payload computing power. While primary applications are Fixed-Satellite Services (FSS) and Broadcast Satellite Services (BSS),
625-412: The use of novel technologies for orbit raising because they operate in orbits that would ordinarily decay too soon to be economically useful. A low Earth orbit requires the lowest amount of energy for satellite placement. It provides high bandwidth and low communication latency . Satellites and space stations in LEO are more accessible for crew and servicing. Since it requires less energy to place
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