Low Cost Hyperspectral Imaging From a Microsatellite

A 100 kg class SSTL microsatellite platform accommodating the Sira Compact High Resolution Imaging Spectrometer (CHRIS) can perform high spectral resolution imaging over multiple wavelengths. Hyperspectral imaging data may be used within a wide variety of applications ranging from precision agriculture and land use, to ocean colour monitoring, coastal and atmospheric studies. CHRIS operates in the 415 to 1050 nm wavelength band, with spectral sampling interval from 2 to 12 nm (depending on wavelength) and is programmable from the ground. Operating at 25 m ground sample distance the instrument can provide information over 19 spectral bands whilst at 50 m ground sample distance, for example, 63 bands can be imaged simultaneously. Flying CHRIS as the main payload on a SSTL microsatellite enables dedicated platform resources to exploit the huge potential of such a payload at low cost. The three-axis stabilised platform can off-point from nadir by ±30° to support accurate target selection. 48 Mbps payload data downlink rates, a 12 Gbyte data storage, and high efficiency GaAs panels for power provision all ensure a good payload duty cycle per orbit. The estimated spacecraft cost is 8.5 million GBP, resulting in affordable constellation options. A constellation of hyperspectral satellites providing high temporal resolution in addition to high spectral resolution could also be used to enhance the infrastructure of the Disaster Monitoring Constellation (DMC). The DMC is currently under construction at SSTL and is due for launch in 2002. This may be implemented either singly, or in constellations, via a ‘plug and play’ constellation approach. This paper describes how low cost hyperspectral imaging may be effectively accomplished using a microsatellite platform and looks at the potential benefits of implementing a series of these microsatellites in a constellation

A High Performance EO Small Satellite Platform (SSTL-300)

This paper describes a new high performance Earth Observation Platform, the SSTL-300, which has been developed to provide customers with a capability that has previously only been available at much higher cost and on larger platforms. This platform offers a 7-year mission lifetime with a very high operational availability. The main payload is a very high-resolution imager (VHRI) with a panchromatic 2.5m ground sampling distance (GSD) channel and four multi-spectral channels offering 5m GSD. The imager swath is 20km in all channels. This imager is an extension of the 4m GSD imager already flying on Beijing-1, which was launched in October 2005. Additional payloads can be accommodated, such as the Medium Resolution Imager (MRI), offering lower resolution of 22m or 32m GSD in four multiple spectral bands with 300km swath width. The 32m MRI has already flown on four previous Disaster Monitoring Constellation (DMC) Missions. High performance geo-location is provided, the performance of which is dependent on the chosen subsystem options. Simultaneous imaging is possible with the VHRI and the MRI and scenes can be as long as 2000km. The image data is compressed on-board, using lossless data compression, for store-and-forward operations. Furthermore, switchable encryption is available, using the Data Encryption Standard (DES), on the TM/TC as well as switchable scrambling on payload data. Near real-time imaging &amp; down-linking is possible for a range of targets close to the ground station. A range of imaging modes are available including: strip mapping, fast response scene capture, stereo imaging, with pitch angles between 10 and 45 degrees to provide digital elevation models, and increased area coverage to provide wide-swath high-resolution imagery of up to 85km. The nominal orbit for the SSTL-300 will be sun-synchronous, with a 10.30am node to provide repeatable global coverage and good lighting conditions. The platform will orbit at approximately 700km, which provides good optimisation for single satellite and constellation revisits. On-board propulsion is included for orbit maintenance.</p

Risk of cerebrovascular disease among 13,457 five‐year survivors of childhood cancer: a population based cohort study

Survivors of childhood cancer treated with cranial irradiation are at risk of cerebrovascular disease (CVD), but the risks beyond age 50 are unknown. In all, 13457 survivors of childhood cancer included in the population‐based British Childhood Cancer Survivor Study cohort were linked to Hospital Episode Statistics data for England. Risk of CVD related hospitalisation was quantified by standardised hospitalisation ratios (SHRs), absolute excess risks and cumulative incidence. Overall, 315 (2.3%) survivors had been hospitalised at least once for CVD with a 4‐fold risk compared to that expected (95% confidence interval [CI]: 3.7‐4.3). Survivors of a central nervous system (CNS) tumour and leukaemia treated with cranial irradiation were at greatest risk of CVD (SHR = 15.6, 95% CI: 14.0‐17.4; SHR = 5.4; 95% CI: 4.5‐6.5, respectively). Beyond age 60, on average, 3.1% of CNS tumour survivors treated with cranial irradiation were hospitalised annually for CVD (0.4% general population). Cumulative incidence of CVD increased from 16.0% at age 50 to 26.0% at age 65 (general population: 1.4‐4.2%). In conclusion, among CNS tumour survivors treated with cranial irradiation, the risk of CVD continues to increase substantially beyond age 50 up to at least age 65. Such survivors should be: counselled regarding this risk; regularly monitored for hypertension, dyslipidaemia and diabetes; advised on life‐style risk behaviours. Future research should include the recall for counselling and brain MRI to identify subgroups that could benefit from pharmacological or surgical intervention and establishment of a case‐control study to comprehensively determine risk‐factors for CVD

Review of a Small Satellite Hyper-spectral Mission

This paper describes a low cost hyper-spectral mission based around the CHRIS instrument that has been developed at Sira Technology Ltd. The CHRIS instrument is flying on the ESA PROBA platform, a small agile satellite of the 100kg class, which was launch in October 2001. The instrument typically acquires more than 300 hyper-spectral images each year via two European ground stations. Today this instrument provides the highest sampling capability of any space-borne hyper-spectral instrument. The main purpose of the instrument is to provide images of land areas, although the applications have extended to include coastal monitoring. The platform provides pointing in both across-track and along-track directions, for target acquisition and slow pitch during imaging (motion compensation). An observational mission has been developed around the facility and this is catering for some 40 or so Principal Investigators (PI) around the world, including Europe, North America, Australia and China with around 100 observational sites

Five Years Orbit Experience of a Small Satellite Hyperspectral Imaging Mission

This paper will summarise the results of a hyperspectral imaging mission that has now completed more than five years in orbit and is providing a wealth of data to Users across the world. The mission has demonstrated, fairly conclusively, that such sophisticated payloads can be implemented successfully on a small satellite platform. The instrument being flown is the Compact High Resolution Imaging Spectrometer (CHRIS) developed within the Optical Payload Group (OPG) of Surrey Satellite Technology Ltd. The instrument is flying on PROBA, a small agile satellite, which was launched in October 2001. The platform provides pointing in both across-track and along-track directions, for target acquisition and multi-angle observations, particularly for measurement of the Bi-directional Reflectance Distribution Function (BRDF) properties of selected targets. The instrument covers a spectral range from 400nm to 1050nm, at £11nm resolution with a spatial sampling interval at perigee of 17m and programmable band sets. The swath width imaged is 13km at perigee. Observations requests for the science mission are selected, prioritised and scheduled into feasible observations on a daily basis. The Mission continues to operate successfully even in its sixth year and demonstrates the success of the mission and the utility of the platform and instrument

A High Performance EO Small Satellite Platform & Optical Sensor Suite

This paper describes a new high performance cost effective Earth Observation Platform, the SSTL-300 and associated optical sensor suite, offering a 7-year mission lifetime with a very high operational availability, for a mission cost an order of magnitude less than commercial high resolution Earth observation spacecraft. The paper will detail the SSTL-300 main payload, a very high-resolution imager with panchromatic multispectral channels. The paper will also outline an additional payload, the Medium Resolution Imager (MRI), which offers the widest swath of any comparable Earth Observation spacecraft. Earth images can be geolocated with high accuracy without the need for ground control points. Simultaneous high- and medium-resolution imaging is possible, coupled with either on-board lossless data compression for store-and-forward operations or near real-time imaging & down-linking for a range of targets close to the ground station. The SSTL-300 offers a range of imaging modes, including: strip mapping, fast response scene capture and stereo imaging offering swath widths up to 60km at high-resolution. Details of the nominal (sun-synchronous) orbit for the SSTL-300 will be provided stressing the balance between single spacecraft and constellation (multiple cooperating spacecraft) performance. The latter requires an accurate and reliable, yet low cost propulsion system which SSTL has developed, but is commonly featured on low cost small spacecraft.</p

A High Performance EO Small Satellite Platform (SSTL-300)

This paper describes a new high performance Earth Observation Platform, the SSTL-300, which has been developed to provide customers with a capability that has previously only been available at much higher cost and on larger platforms. This platform offers a 7-year mission lifetime with a very high operational availability. The main payload is a very high-resolution imager (VHRI) with a panchromatic 2.5m ground sampling distance (GSD) channel and four multi-spectral channels offering 5m GSD. The imager swath is 20km in all channels. This imager is an extension of the 4m GSD imager already flying on Beijing-1, which was launched in October 2005. Additional payloads can be accommodated, such as the Medium Resolution Imager (MRI), offering lower resolution of 22m or 32m GSD in four multiple spectral bands with 300km swath width. The 32m MRI has already flown on four previous Disaster Monitoring Constellation (DMC) Missions. High performance geo-location is provided, the performance of which is dependent on the chosen subsystem options. Simultaneous imaging is possible with the VHRI and the MRI and scenes can be as long as 2000km. The image data is compressed on-board, using lossless data compression, for store-and-forward operations. Furthermore, switchable encryption is available, using the Data Encryption Standard (DES), on the TM/TC as well as switchable scrambling on payload data. Near real-time imaging & down-linking is possible for a range of targets close to the ground station. A range of imaging modes are available including: strip mapping, fast response scene capture, stereo imaging, with pitch angles between 10 and 45 degrees to provide digital elevation models, and increased area coverage to provide wide-swath high-resolution imagery of up to 85km. The nominal orbit for the SSTL-300 will be sun-synchronous, with a 10.30am node to provide repeatable global coverage and good lighting conditions. The platform will orbit at approximately 700km, which provides good optimisation for single satellite and constellation revisits. On-board propulsion is included for orbit maintenance.</p