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Bengaluru: The Indian Space and Research Organisation (ISRO) is all set to launch five British satellites at one go on Friday, in what is being billed as its biggest commercial launch so far.
The countdown has begun at the Sriharikota launch pad for the PSLV-C28 rocket, which will carry five satellites - load of over 1440 kg - for the UK. Three of these satellites are earth observations satellites while the other two are technology demonstrators.The launch is scheduled for 9.58 pm.
PSLV, in its 30th mission, would launch three identical DMC3 optical earth observation satellites, built by Surrey Satellite Technology Limited (SSTL), United Kingdom, and two auxiliary satellites. The three DMC3 satellites, each weighing 447 kg, will be launched into a 647 km Sun-Synchronous Orbit (SSO) using the high-end version of PSLV-XL.
DMC3: The Mission
Under a £110m contract SSTL is providing three SSTL-300S1 satellite platforms, a new smallsat design which provides unparalleled 1 metre high resolution imagery with high speed downlink and 45 degree off-pointing.
The three satellites will form a new constellation, DMC3, with daily revisit times which is crucial for change detection, disaster monitoring and response planning, and essential for acquiring cloud-free imagery.
The SSTL-300S1 satellite design features advanced avionics and optical systems that make it possible to perform several different types of imaging such as mapping terrain, strip imaging and mosaic imaging for wide areas.
Beijing-based company, 21AT, will lease 100% of the imaging capacity of the three satellites.
DMC-3 stands for Disaster Monitoring Constellation 3 and represents three high-resolution optical Earth imaging spacecraft owned and operated by DMCii (DMC International Imaging), headquartered in Guildford, UK. The company is a subsidiary of Surrey Satellite Technology Ltd., the manufacturer of the three identical DMC-3 satellites flying in a 630-Kilometer Sun-Synchronous Orbit. SSTL is a world leader in small-satellite technology ranging from satellite components, bus platforms, payloads and complete satellites for operation in Earth imaging, technology demonstrations and a range of other of applications.
The business model of DMCii calls for the company operating the DMC satellites and leasing their capacity to commercial customers, providing daily access opportunities to any given area on Earth. The first customer to sign with DMCii was 21AT, the Twenty First Century Aerospace Technology Company Ltd. in Beijing, China. Signed in 2011, the contract includes the lease of the entire capacity of the first three DMC satellites with a contract time of seven-years.
The entire DMC-3 constellation has been designed to meet 21AT’s Earth observation requirements of a one-meter ground resolution in the panchromatic and three-meter resolution in the multispectral bands. Under the contract, all satellite related tasks are executed by DMCii including observation scheduling and satellite operation while 21AT makes observation requests and receives processed data products.
The two companies have prior business experience through the Beijing-1 satellite that has been operated by SSTL since 2005 and was used to provide Earth observation products to 21AT and the Chinese government for environmental monitoring, resource management, agriculture, urban planning, disaster management and a number of other purposes.
Spacecraft Overview
The three DMC-3 satellites are based on the SSTL-300 S1 spacecraft platform that builds on the smaller SSTL platforms such as the SSTL-100 and –150 using a number of heritage components in a larger, more-capable platform that can host imaging payloads achieving sub-meter resolution. Prior to DMC-3, SSTL-300 was flown by the NigeriaSat-2 satellite that met the planned requirements and showed an excellent performance after its 2011 launch.
The S1 addition to the SSTL-300 bus represents a composite imager barrel that is part of the imaging payload, giving the satellite a length of over 2.5 meters.Weighing in at around 350 Kilograms, each DMC-3 spacecraft consists of two major components - a platform assembly hosting the various satellite subsystems and a 150-Kilogram payload assembly that facilitates the optical imaging system and the imager barrel. The core of the satellite structure is a cylinder that is comprised of several segments - beginning in the aft of the spacecraft with a Lower Link Assembly that interfaces with the launch vehicle adapter and a Lower Barrel that is connected to the Upper Barrel Assembly by a Central Bulkhead which can provide mounting structures for various systems including payload structures.
The Upper Barrel Assembly consists of laminated pre-impregnated Carbon Fiber Reinforced Polymer (CFRP) with several circumferential L-profile CRFP ring cleats and titanium fittings that provide the attachment points for the payload hardware. The Central Bulkhead is responsible for the structural connection between the payload and the satellite platform in addition to load transfer during launch and dampening of vibrations originating within the satellite platform systems.
The bulkhead includes two bearing assemblies of two- and three-degree of freedom configurations. It consists of similar materials as the Upper Barrel, but given the more significant loads of the bulkhead, its structural components are of increased thickness. The Lower Barrel resembles the Upper Barrel in appearance, but is shorter and uses less-thick material.
Optical capability :
The instrument covers five spectral bands – a panchromatic band at 450 to 650 nanometers achieving a one-meter ground resolution and four multispectral bands with a four-meter resolution: 440-510nm (blue), 510-590nm (green), 600-670nm (red), and 760-910nm (near infrared).
Focus control within the telescope is provided by a moving corrector lens that is located near the center of the primary mirror. Given the more stringent requirements of the S1 payloads in terms of focus lens alignment, linear position and stability, the old design employed by NigeriaSat was no longer viable and a completely new system was developed, referred to as Relay Lens Assembly.
The overall purpose of the RLA is the placement of the focusing lens along the optical axis to ensure the Earth image is focused with the specific depth of focus of the focal plane. To achieve the required image quality, the Relay Lens Assembly has to be capable of placing the focusing lens with an accuracy better than 5 micrometers along a travel distance of 10 millimeters. The lens has to provide an extremely high positional stability in the various environments of launch, thermoelastic loads and the micro-vibration environment on the satellite.
The parallel shift of the lens optical axis has to be less than 5 micrometers and the tilt of the lens against the telescope’s optical axis can be no greater than 15arcsec. Optical decentration can be no greater than 10 micrometers. The focusing lens is 14.8 centimeters in diameter and utilizes a stepper motor, and stainless steel ball screw to drive the lens carriage along the three linear ball bushing shafts. The lens is truncated at two sides with a width of 11 centimeters and it resides within a titanium lens cell which is bonded into place on the titanium lens carriage mechanism.
A non-contacting linear decoder provides independent feedback of the motion and position of the focusing lens.The S1 instrument uses five linear detector arrays separated in the along track direction within the common focal plane of the telescope keeping with a pushbroom-type design that images the ground area as it passes the different arrays. Time Delayed Integration is employed for the read-out of the detectors that have an excellent Signal to Noise ratio of 100:1 so that imaging of low-albedo targets poses no challenge to the S1 instrument.
A Chinese Company hires a British Firm to ( Build and .. ) Launch its Satellites from India.
Jai Ho !!
The countdown has begun at the Sriharikota launch pad for the PSLV-C28 rocket, which will carry five satellites - load of over 1440 kg - for the UK. Three of these satellites are earth observations satellites while the other two are technology demonstrators.The launch is scheduled for 9.58 pm.
PSLV, in its 30th mission, would launch three identical DMC3 optical earth observation satellites, built by Surrey Satellite Technology Limited (SSTL), United Kingdom, and two auxiliary satellites. The three DMC3 satellites, each weighing 447 kg, will be launched into a 647 km Sun-Synchronous Orbit (SSO) using the high-end version of PSLV-XL.
DMC3: The Mission
Under a £110m contract SSTL is providing three SSTL-300S1 satellite platforms, a new smallsat design which provides unparalleled 1 metre high resolution imagery with high speed downlink and 45 degree off-pointing.
The three satellites will form a new constellation, DMC3, with daily revisit times which is crucial for change detection, disaster monitoring and response planning, and essential for acquiring cloud-free imagery.
The SSTL-300S1 satellite design features advanced avionics and optical systems that make it possible to perform several different types of imaging such as mapping terrain, strip imaging and mosaic imaging for wide areas.
Beijing-based company, 21AT, will lease 100% of the imaging capacity of the three satellites.
DMC-3 stands for Disaster Monitoring Constellation 3 and represents three high-resolution optical Earth imaging spacecraft owned and operated by DMCii (DMC International Imaging), headquartered in Guildford, UK. The company is a subsidiary of Surrey Satellite Technology Ltd., the manufacturer of the three identical DMC-3 satellites flying in a 630-Kilometer Sun-Synchronous Orbit. SSTL is a world leader in small-satellite technology ranging from satellite components, bus platforms, payloads and complete satellites for operation in Earth imaging, technology demonstrations and a range of other of applications.
The business model of DMCii calls for the company operating the DMC satellites and leasing their capacity to commercial customers, providing daily access opportunities to any given area on Earth. The first customer to sign with DMCii was 21AT, the Twenty First Century Aerospace Technology Company Ltd. in Beijing, China. Signed in 2011, the contract includes the lease of the entire capacity of the first three DMC satellites with a contract time of seven-years.
The entire DMC-3 constellation has been designed to meet 21AT’s Earth observation requirements of a one-meter ground resolution in the panchromatic and three-meter resolution in the multispectral bands. Under the contract, all satellite related tasks are executed by DMCii including observation scheduling and satellite operation while 21AT makes observation requests and receives processed data products.
The two companies have prior business experience through the Beijing-1 satellite that has been operated by SSTL since 2005 and was used to provide Earth observation products to 21AT and the Chinese government for environmental monitoring, resource management, agriculture, urban planning, disaster management and a number of other purposes.
Spacecraft Overview
The three DMC-3 satellites are based on the SSTL-300 S1 spacecraft platform that builds on the smaller SSTL platforms such as the SSTL-100 and –150 using a number of heritage components in a larger, more-capable platform that can host imaging payloads achieving sub-meter resolution. Prior to DMC-3, SSTL-300 was flown by the NigeriaSat-2 satellite that met the planned requirements and showed an excellent performance after its 2011 launch.
The S1 addition to the SSTL-300 bus represents a composite imager barrel that is part of the imaging payload, giving the satellite a length of over 2.5 meters.Weighing in at around 350 Kilograms, each DMC-3 spacecraft consists of two major components - a platform assembly hosting the various satellite subsystems and a 150-Kilogram payload assembly that facilitates the optical imaging system and the imager barrel. The core of the satellite structure is a cylinder that is comprised of several segments - beginning in the aft of the spacecraft with a Lower Link Assembly that interfaces with the launch vehicle adapter and a Lower Barrel that is connected to the Upper Barrel Assembly by a Central Bulkhead which can provide mounting structures for various systems including payload structures.
The Upper Barrel Assembly consists of laminated pre-impregnated Carbon Fiber Reinforced Polymer (CFRP) with several circumferential L-profile CRFP ring cleats and titanium fittings that provide the attachment points for the payload hardware. The Central Bulkhead is responsible for the structural connection between the payload and the satellite platform in addition to load transfer during launch and dampening of vibrations originating within the satellite platform systems.
The bulkhead includes two bearing assemblies of two- and three-degree of freedom configurations. It consists of similar materials as the Upper Barrel, but given the more significant loads of the bulkhead, its structural components are of increased thickness. The Lower Barrel resembles the Upper Barrel in appearance, but is shorter and uses less-thick material.
Optical capability :
The instrument covers five spectral bands – a panchromatic band at 450 to 650 nanometers achieving a one-meter ground resolution and four multispectral bands with a four-meter resolution: 440-510nm (blue), 510-590nm (green), 600-670nm (red), and 760-910nm (near infrared).
Focus control within the telescope is provided by a moving corrector lens that is located near the center of the primary mirror. Given the more stringent requirements of the S1 payloads in terms of focus lens alignment, linear position and stability, the old design employed by NigeriaSat was no longer viable and a completely new system was developed, referred to as Relay Lens Assembly.
The overall purpose of the RLA is the placement of the focusing lens along the optical axis to ensure the Earth image is focused with the specific depth of focus of the focal plane. To achieve the required image quality, the Relay Lens Assembly has to be capable of placing the focusing lens with an accuracy better than 5 micrometers along a travel distance of 10 millimeters. The lens has to provide an extremely high positional stability in the various environments of launch, thermoelastic loads and the micro-vibration environment on the satellite.
The parallel shift of the lens optical axis has to be less than 5 micrometers and the tilt of the lens against the telescope’s optical axis can be no greater than 15arcsec. Optical decentration can be no greater than 10 micrometers. The focusing lens is 14.8 centimeters in diameter and utilizes a stepper motor, and stainless steel ball screw to drive the lens carriage along the three linear ball bushing shafts. The lens is truncated at two sides with a width of 11 centimeters and it resides within a titanium lens cell which is bonded into place on the titanium lens carriage mechanism.
A non-contacting linear decoder provides independent feedback of the motion and position of the focusing lens.The S1 instrument uses five linear detector arrays separated in the along track direction within the common focal plane of the telescope keeping with a pushbroom-type design that images the ground area as it passes the different arrays. Time Delayed Integration is employed for the read-out of the detectors that have an excellent Signal to Noise ratio of 100:1 so that imaging of low-albedo targets poses no challenge to the S1 instrument.
A Chinese Company hires a British Firm to ( Build and .. ) Launch its Satellites from India.
Jai Ho !!
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