“Each of the SENTINEL-2 satellites weighs approximately 1.2 tonnes, and is designed to be compatible with small launchers like VEGA and ROCKOT. The satellite lifespan is 7.25 years, which includes a 3 month in-orbit commissioning phase. Batteries and propellants have been provided to accommodate 12 years of operations, including end of life de-orbiting manoeuvres.
Two identical SENTINEL-2 satellites will operate simultaneously, phased at 180° to each other, in a sun-synchronous orbit at a mean altitude of 786 km. The position of each SENTINEL-2 satellite in its orbit will be measured by a dual-frequency Global Navigation Satellite System (GNSS) receiver. Orbital accuracy will be maintained by a dedicated propulsion system.
The SENTINEL-2 satellite system is being developed by an industrial consortium led by Astrium GmbH (Germany). Astrium SAS (France) is responsible for the MultiSpectral Instrument (MSI).
The MSI works passively, by collecting sunlight reflected from the Earth. New data is acquired at the instrument as the satellite moves along its orbital path. The incoming light beam is split at a filter and focused onto two separate focal plane assemblies within the instrument; one for Visible and Near-Infra-Red (VNIR) bands and one for Short Wave Infra-Red (SWIR) bands . The spectral separation of each band into individual wavelengths is accomplished by stripe filters mounted on top of the detectors.”
“The U.S. commercial SpaceX Dragon cargo craft was released from the International Space Station’s Canadarm2 robotic arm in the early hours of March 19, after spending more than three weeks at the orbital outpost. During that time, the crew onboard transferred onto the station several tons of supplies and scientific investigations delivered by Dragon. Expedition 50 crew members Thomas Pesquet of ESA (European Space Agency) and Commander Shane Kimbrough of NASA bid farewell to Dragon as the resupply craft moved to a safe distance away from the complex for its deorbit engine firing and a parachute-assisted splashdown in the Pacific. Dragon is returning critical science experiments for investigators back on the Earth.”
“The Wideband Global SATCOM system (WGS) is a high capacity satellite communications system planned for use in partnership by the United States Department of Defense (DoD) and the Australian Department of Defence. The system is composed of the Space Segment satellites, the Terminal Segment users and the Control Segment operators.
DoD wideband satellite communication services are currently provided by a combination of the existing Defense Satellite Communications System (DSCS) and Global Broadcast Service (GBS) satellites. According to United Launch Alliance, quoted on Spaceflight Now, “A single WGS spacecraft has as much bandwidth as the entire existing DSCS constellation.”
The constellation of WGS satellites increases the communications capabilities of the militaries of the United States, Canada, and Australia by providing additional bandwidth and communications capabilities for tactical command and control, communications, and computers; intelligence, surveillance, and reconnaissance (C4ISR); battle management; and combat support information. Canada has also signed on to become a partner.
WGS also augments the current Ka-band Global Broadcast Service (on UHF F/O satellites) by providing additional information broadcast capabilities as well as providing new two-way capability on that band. The combination of the Wideband Global Satellites, DSCS satellites, GBS payloads, wideband payload and platform control assets, and earth terminals operating with them has been referred to as the Interim Wideband System (IWS). It provides services to the US DoD and Australian Department of Defence. The IWS System supports continuous 24-hour-per-day wideband satellite services to tactical users and some fixed infrastructure users. Limited protected services will be provided under conditions of stress to selected users employing terrestrial modems capable of providing protection against jamming.
The WGS satellites will complement the DSCS III Service Life Enhancement Program (SLEP) and GBS payloads and will offset the eventual decline in DSCS III capability. WGS will offer 4.875 GHz of instantaneous switchable bandwidth, thus each WGS can supply more than 10 times the capacity of a DSCS III Service Life Enhancement Program (SLEP) satellite. Once the full constellation of 6 WGS satellites is operational, they will replace the DSCS system. WGS-1 with its 2.4 Gbit/s wideband capacity, provided greater capability and bandwidth than all the DSCS satellites combined.
Operation and usage of the system is broken into 3 segments.
The end users of the communication services provided by the WGS are described by the DoD as the terminal segment. Users include the Australian Defence Force and U.S. Army ground mobile terminals, U.S. Navy ships and submarines, national command authorities for the nuclear forces, and various national security/allied national forces. Additionally, the Air Force Satellite Control Network will also use the WGS in a similar manner as the DSCS III constellation is used to route ATM packets through the DISA “cloud” to establish command and control streams with various satellite constellations. One of the emerging applications is SATCOM-ON-The-Move which is now being extensively used on the military tactical vehicles for Blue Force Tracking and C3 missions.
The satellite operators in charge of commanding and monitoring the satellite’s bus and payload systems as well as managing the network operating over the satellite are the control segment. Like the DSCS constellation that WGS will replace, spacecraft bus will be commanded by the 3rd Space Operations Squadron of Schriever AFB, Colorado. Payload commanding and network control will be handled by the Army 53rd Signal Battalion headquartered at nearby Peterson AFB, Colorado with subordinate elements A Co. at Fort Detrick, Maryland, B Co. at Fort Meade, Maryland, E Co. at Fort Buckner, Okinawa Japan, C Co. Landstuhl Germany, and, D Co. Wahiawa, Hawaii.
The primary contractor for the satellites themselves is Boeing Satellite Development Center, which is building them around the Boeing 702 satellite platform. Originally five satellites were planned. On October 3, 2007, Australia’s Department of Defence announced that the country would fund a sixth satellite in the constellation. Once in their orbits at an altitude of 22,300 mi (35,900 km), each will weigh approximately 7,600 lb (3,400 kg). The program intends to use both the Delta IV and the Atlas V as launch vehicles. The Air Force Space Command estimates each satellite will cost approximately US$300 million.”
“SmallGEO is a multipurpose satellite platform capable of accommodating a wide range of commercial telecommunications payloads and missions, from TV broadcasting to multimedia applications, Internet access and mobile or fixed services in a wide range of frequency bands.
Its new, modular and flexible design boosts European industry’s ability to play a significant role in commercial satcoms by easing entry into the lower-mass telecom satellite market.
The platform was developed by OHB System (DE) under ESA’s Advanced Research in Telecommunication Systems (ARTES) programme. SmallGEO is the first ESA programme with OHB System AG as the industrial prime. Its first flight and in-orbit demonstration will be with the Hispasat 36W-1 telecom satellite.”
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