SSTL’s Optical Payloads Group has commenced a science project that will study fluorescent emissions from vegetation using a remote sensing instrument designed to fly onboard a small satellite.

Carbon dioxide (CO2) is notoriously difficult to measure and so far it has been impossible to calculate the uptake of the Earth’s CO2 sinks with sufficient accuracy for scientific analysis – for example hindering our ability to monitor the efficacy of CO2 mitigation policies. There is an urgent need to improve data on the natural CO2 uptake of vegetation in order to improve our understanding of its influence on the Earth's carbon cycle and its potential to suppress today’s increasing atmospheric CO2 concentration. Even minor changes in ecosystem-scale photosynthesis can have a significant affect on the global carbon balance.

Satellites have made a huge difference to our knowledge of vegetation conditions, but until now most of that information has come from remotely sensing reflected sunlight with multi-spectral Earth observation satellites. There is, however, one additional source of information about vegetation in the optical and near-infrared wavelength range. During photosynthesis part of the energy absorbed by chlorophyll is not used for carbon fixation, but re-emitted at longer wavelengths as fluorescence.

'The European Space Agency (ESA) Fluorescence Explorer (FLEX), which is a candidate for the Earth Explorer 8 missions, aims to provide global maps of vegetation fluorescence that can be converted into an indicator of photosynthetic activity. These data would improve our understanding of how much carbon is stored in plants and their role in the carbon and water cycles.

SSTL will identify one optimised design of an instrument under a 400k€ contract from ESA that will detect the weak radiation emitted in this specific wavelength range from space. The Fluorescence Imaging Spectrometer (FIMAS) instrument will be compact enough to fly on a small satellite as a precursor to the primary instrument onboard FLEX.

Gordon Hopkinson, from SSTL's Optical Payloads Group was a physicist who made a notable contribution to the development of today’s space imaging systems

Gordon Hopkinson was one of the world’s experts in the physics of optical detectors used in a wide range of applications from digital cameras through to international space missions and even mobile phones. For three decades he was involved in detailed analysis and modelling of solid state cameras and contributed significantly to the research of their use in a wide range of applications from X-ray mammography, the mapping of the stars to the search for dark matter.

His ability to undertake detailed measurements, identify new phenomena and develop the underlying mathematical models was second to none. Gordon was also a very kind person, modest and with a high standard of integrity. He will be sorely missed by friends and colleagues both within the UK and across the world.

Hopkinson began his research at Manchester University with spells at Durham and Leicester undertaking research into astronomy, such as spectral investigations of comets and observations of zodiacal dust. His move to Leicester coincided with the emergence of the new and revolutionary solid state detectors based on silicon chips, known as Charge Coupled Devices (the heart of today’s digital cameras). The first of these were developed in the UK in 1972 by EEV (subsequently known as e2v). The Charge Coupled Devices (CCD) would replace the previous bulky vacuum tube detectors and eventually give rise to the demise of photographic film.

At Leicester University Hopkinson developed ground breaking techniques for achieving low noise performance from CCDs and together with David Lumb wrote the definitive paper on the subject. These techniques were subsequently applied to the new breed of space imaging missions and are still used to this day. He has several publications in this field and numerous citations. The research that Hopkinson undertook at Leicester would shape his professional life.

In 1983 Hopkinson moved to the Sira research and development organisation in Kent and immediately found that his expertise in CCDs was essential to fully exploit the capabilities of these devices in a range of new and highly demanding space instrumentation. Hopkinson’s first task was to support the development of the state of the art star trackers and a star mapper for a X-ray satellite mission called ROSAT, funded by the German Space Agency and launched in 1990. The ROSAT mission undertook an all-sky survey of x-ray emitting objects and led to a detailed morphology of supernova remnants and clusters of galaxies. ROSAT operated until 1999. Similar applications soon arose in the use of CCDs for first inter-satellite laser communications system (SILEX), oceanographic monitoring (MERIS) and the measurement of ozone from space (GOMOS), all of which are still in operation today providing invaluable information and capabilities to the European science community.

Hopkinson’s key expertise was not only in achieving high performance from solid state detectors but also analysing the complex effects arising from the harsh space radiation environment of protons and gamma rays. This was a special interest that led to international recognition. Of particular note was a request by the European Space Agency (ESA) for Hopkinson to undertake detailed radiation analysis on a new but highly demanding astrometric mission called GAIA. This mission aims to create the largest and most precise three dimensional chart of our Galaxy taking measurements of about one billion stars.

Hopkinson was a recognised international authority in his field of research and has published many papers, participated by invitation in NASA, ESA and Japanese working groups and acted as chairman at many international conferences. He not only received many credits for his work but through his considerable reputation and expertise sat on the Awards Committee of the Institute of Electrical & Electronic Engineers (IEEE).

Hopkinson moved with the Sira Space Group to Surrey Satellite Technology Ltd in 2006, the world leading small satellite manufacturer, and set up new facilities to continue his work. This has included continued research into detectors for space missions such as Solar Orbiter, to produce images of the Sun at an unprecedented resolution, EarthCARE, a joint European-Japanese mission addressing the need for a better understanding of the Earth’s climate, and EUCLID, with the primary goal to map and characterise the geometry of the dark universe, a feature of considerable interest to the science community.

Gordon Robert Hopkinson was born in 1952, the only child of Jessie and Alan and brought up in Nottingham. He was educated at Forest Fields Grammar School, Nottingham and went onto read Physics at Manchester University graduating with first-class honours in 1973, he then undertook a PhD graduating in 1977.

Gordon loved barbeques, walking, history, crosswords and real ale. Most family holidays involved incorporating as many of these as possible. Top of the list were camping holidays in France with barbeques every night and walking holidays in Derbyshire, where the route would be planned according to the beer.

He is survived by his wife, Jacqui, whom he married in 1980 and by their two daughters and son.

Gordon Hopkinson, detector physicist, was born on July 4th 1952. He died on September 12th 2010, aged 58.

SSTL’s Optical Payload Group is currently building two Dynamic Multi Star-field Simulators (DMSS) at its Sevenoaks facility that will be used to test star trackers that will be flown in space under simulated operating conditions here on Earth.

Star trackers are an essential subsystem in any satellite, providing information that allows the spacecraft's on board computer to determine its orientation or “pointing” at any point in time.

They work by taking an image of a region of the sky using a specially designed optical camera, and comparing successive images to determine how much the orientation of the satellite has drifted.

This information is then sent to an attitude control system that corrects for the drift by using on-board thrusters or other motion-generating devices to maintain the correct satellite pointing.

Any time a satellite is manoeuvred in orbit, the pointing information from star trackers is vital to the spacecraft’s control systems. For example, solar panels must be aligned to capture the maximum available light from the Sun, and communications antennae pointed towards the Earth.

Star trackers are now available that operate in autonomous modes. These units are able to dynamically monitor the star fields in orbit and provide correction information back to the satellite to counteract adverse platform manoeuvres, such as slews and spins, which is particularly useful in the early stage of mission operations or following a major system failure.

To test these units on the ground prior to launch, it is essential to present the star trackers with a dynamically varying star field. This is where the DMSS comes in.

Continue reading "Simulators prepare star trackers for spaceflight"

For several months Cliff Slogrove from SSTL’s Optical Payloads Group in Sevenoaks has lead a double life. When he wasn’t helping build optical payloads for satellites, he was helping schoolchildren from the nearby Langley Park School for Boys (LPSB) in Beckenham, Kent prepare for the Shell Eco-marathon Youth Challenge UK.

The Shell Eco-Marathon Youth Challenge UK is an annual fuel economy competition organised by Shell Global Solutions. Competitors from schools and youth teams construct a vehicle that meets the required safety aspects and run it around a circuit using as little fuel as possible. The best designs consider aspects of aerodynamics, rolling resistance, engine efficiency and driving techniques to achieve the highest fuel economy.

This year’s event took place 2nd-3rd July 2008 at the Rockingham Motor Racing Circuit. The LSPB team comprising 14 boys, 3 teachers and Cliff came fourth in the 17-strong schools class.

Their Honda GX31-engined Spirit 2 car achieved 646 miles per gallon, breaking the school’s previous record of 400.6 by 246 mpg.

Unfortunately, after that things started to go a little wrong for the team. The next run Spirit 2’s engine failed after 5 laps and the drive chain came off. Their second car, Spirit 1, had a run of 333mpg and improved to 359mpg but couldn’t compete with the likes of “Green Meanie”.

The students had fitted a GPS to Spirit 2 so they could see where it was on the track and the speeds it was doing. The speeds recorded were 9 to 25 miles per hour, with 2 burns of the engine per lap. The max speed was 35+ miles per hour!

Team LPBS won the “spirit of the event” award by lending our spare engine to one team and our spare carb to another.

The teams had to perform in the media spotlight, TV show News Round was filming and BBC Northampton radio even interviewed student Matt Shirley.