Space blog

SSTL have successfully completed the Critical Design Review (CDR) for NigeriaSat-2. This review is of the finalised design of the NigeriaSat-2 spacecraft and ground segment and plans for the full satellite manufacture. The 300 kg satellite will provide Nigeria with valuable geographically referenced high-resolution satellite imaging for mapping, water resource management, agricultural land use, population estimation, health hazard monitoring and disaster mitigation and management. The higher resolution optical payload will enable Nigeria to join the second generation Disaster Monitoring Constellation (DMC).

This is an exciting period for the small satellite manufacturer, because NigeriaSat-2 will use the new, more agile SSTL-300 Earth Observation satellite platform.

Customer representatives from the National Space Research & Development Agency (NASRDA) have attended seven days of meetings at SSTL's headquarters in Guildford as part of the CDR.

Meanwhile during the third week in November, Nigeria's training satellite turned "real" satellite, codenamed NX has passed its Preliminary Design Review (PDR) with flying colours. The Nigerian Know How Transfer and Training (KHTT) team carried out the PDR for NX, which was was originally planned purely for training engineers as part of the NigeriaSat-2 programme. The PDR marks a significant milestone for the project and reflects the confidence of Nigeria's National Space Research And Development Agency (NASDRA) in the continued development of their engineers under the SSTL KHTT programme.

Back in August, the Sky at Night invited Martin Sweeting down to Patrick Moore's home in Sussex to film an interview for a programme celebrating 50 years of space. This program will also include a discussion of SSTL's lunar studies with Andy Phipps.

The Sky at Night
Dr Chris Lintott finds out how British technology is leading the way in satellite science, while Sir Patrick Moore investigates the threat from space debris that astronauts face in space.

For anyone that would like to tune in, the Sky at Night will be broadcast this Sunday evening, 2nd December, on BBC 4 at 20:30.

Algeria is celebrating the 5th birthday of its first satellite, ALSAT-1 this week.

Last summer, a heatwave struck Algeria bringing with it temperatures of up to 50 degrees Celsuis. This dryed out the North African landscape, leading to forest fires in several forests.

The Batna region, which has some of the most densely forested regions in Algeria, was one of the worst affected areas. In particular, places like Djebel Belezma and Beni Fedhla were stricken by severe conflagrations accented by sirocco winds blowing at more than 80 kph.

The fire has destroyed a significant part of the forests in the Batna region. For example, only this summer, fires have destroyed over 8000 hectares in Djebel Kimmel and in the area of Arris.

Forest fires: astronomical figures



Algeria used the SSTL-built ALSAT-1 satellite in a study to monitor forest fires and evaluate the damage caused and assess the forests’ ability to regenerate.



The location referenced (geospatial) images from Algeria’s own satellite were supplemented where required with additional Disaster Monitoring Constellation (DMC) data where required.

How satellite imaging is applied
The images were acquired from areas of interest are first pre-processed using the ENVI image processing software, these are then analysed and finely processed for later use. This results in cartographical (maps) that are easy to read with the human eye. The maps are then used to identify the various forest formations and the impact that this summer’s (2007) fires have had on them.
Both supervised classification and the vegetation index (NDVI) methods were used to determine the different forest formations and to deduct the fire impact on them. This methodology has allowed the Centre National des Techniques Spatiales (CNTS) to accurately assess the destruction of forest fires in the north of Algeria during this year’s (2007) campaign.

A pioneering experiment was launched onboard UK-DMC in 2003, that uses signals reflected from the GPS signals already in orbit to monitor the weather at sea. The joint team experiment team, comprising SSTL and the University of Surrey members has now succeeded for the first time in capturing a Galileo signal from SSTL's GIOVE-A satellite reflected off the ocean surface. Although the signal was weak, because the equipment is optimised for receiving GPS signals, this is an important achievement demonstrating the potential for determining the weather at sea with remote sensing satellites.

What's more, it seems this new development is well timed - the Partnership for Observation of the Global Oceans (POGO), a distinguished partnership of international scientists is calling for a stable network of satellites for surveying vast extents of the surface of the ocean to enable societal benefits' (see POGO release, BBC).

Coincidentally, HRH Duke Of Kent was visiting SSTL at the time and was given a whistlestop tour which touched on "bistatic radar" and "forward scatterometry" (keep reading...).

The pioneering GPS Reflectometry Experiment was launched onboard SSTL’s UK-DMC satellite in 2003 to demonstrate the use of GPS reflections to determine the roughness of the ocean, using a method called “bistatic radar” or “forward scatterometry”. This experiment has now successfully detected a Galileo satellite navigation signal reflected by the ocean’s surface. GIOVE-A, the first Galileo demonstration satellite, also built by SSTL, was commissioned by the European Space Agency and has been transmitting prototype Galileo signals since its launch in December 2005.

In early November, 20 seconds of data were captured in orbit above the Arafura Sea, north of Australia, and downloaded to Surrey for processing. Whilst the orbiting experiment on UK-DMC is not optimised for Galileo signals, enough of the reflected signal energy was received to allow the detection and plotting of the weak signal after processing by University of Surrey PhD student, Philip Jales. The shape of the reflection gives an indication of the sea roughness and hence the weather at that place and time, where the wind speed was around 14 mph (22 km/h).

SSTL's Global Navigation Satellite Systems (GNSS) / GPS head, Dr Martin Unwin (centre left) explained

“This is an important achievement in remote sensing and demonstrates the potential offered by Galileo for scientific purposes. A constellation of small satellites could be deployed at low cost to take measurements over the oceans where there are large gaps in forecast knowledge at present. An improved measurement system in space could be used to warn mariners of storms and to provide data for global climate change models - potentially even to detect Tsunamis.”

Dr Unwin is also enthusiastic about benefits of inter-system cooperation:

“Signals from Galileo, in conjunction with GPS and the Russian and Chinese systems, Glonass and Compass, can all be used as part of a new tool for ocean sensing. The future high bandwidth signals transmitted by Galileo, in particular, will enable higher resolution measurements of special interest to scientists, for example, in resolving wave heights”

GPS Reflectometry is of great interest to engineers and scientists as a cost effective means of remote sensing. Firstly, a special transmitter is not required because GPS signals are already broadcast to the Earth 24 hours a day. Also, a satellite dedicated to GPS reflectometry would only need to carry a modified miniaturised GPS/Galileo receiver and an antenna, which could potentially be accommodated on a tiny 10 kg satellite platform at low cost, enabling multiple satellites on a single launch.



The concept is shown in the animation shown to the left (this is freely available and can be embedded into blogs from YouTube).

The UK-DMC Reflectometry Experiment has also previously been used to detect GPS signals reflected off ice and, surprisingly, dry land. The value of these measurements has yet to be fully explored but they may be used as inputs for climate modelling.

A future revision of the experiment, the “GNSS Reflectometry Instrument” is now being designed at Surrey with a view to flight on a future satellite mission. It is being designed specifically to receive Galileo signals as well as those from GPS, with the intention of real time processing. Dr Unwin's final words on the matter, “The sooner Galileo is up and transmitting the better”