"We feel this is a unique and valuable contribution to the science community," said Dave Hodgson, managing director of DMC International Imaging Ltd (DMCii), which operates the satellites.
"We look forward to supporting some deserving scientific research that will contribute to our knowledge of the Earth and our impact on its resources."
The DMC satellites work in partnership to picture large areas - up to 360,000 square kilometres - in a very short space of time.
Nowhere is the need to improve our knowledge more pressing than in the monitoring of climate change
DMC International Imaging Ltd
They orbit in sequence, taking turns to scan the next strip of land or sea.
Crucially, their orbits enable them to make a daily revisit to any given target site. Such frequent visits allow them to monitor subtle changes in the landscape, and make the most of cloud-free moments.
Each spacecraft is equipped with multi-spectral sensors, which are tailored to detect changes in vegetation - a valuable tool for a range of Earth observation projects.
In Afghanistan, the satellites keep an eye on poppy crops - helping the UK government to anticipate the opium trade.
In Afghanistan, the satellites monitor the poppy crops (shown in red)
But they also monitor the wheat crops, allowing the Afghan government to anticipate potential food shortages.
In Botswana, the DMC has tracked the encroachment of farmers' fields onto elephant grazing lands. This helps to predict the likelihood of dangerous conflicts between elephants and humans.
In Brazil, the satellites take regular pictures of the Amazon basin, enabling the government to monitor deforestation.
And in Alberta, Canada, they are helping farmers to boost crop yields by carrying out remote sensing of soil nutrient levels. The measurements help determine the type and volume of fertiliser required for different soil types.
The two new satellites, Deimos-1 and UK-DMC2, will offer far higher resolution images (22m) than the current DMC quintet (32m).
They were designed and built by the UK's Surrey Satellite Technology Ltd (SSTL).
The 10 winning bids for free use of the satellites will be split evenly between researchers from Spain, home of Deimos-1, and the UK, home of UK-DMC2.
Entries will be judged on the value of their contribution to international environmental research, by a panel chaired by Professor Alan O'Neil, from the UK National Centre for Earth Observation (NCEO).
"Nowhere is the need to improve our knowledge more pressing than in the monitoring of climate change," said Mr Hodgson.
"The Intergovernmental Panel on Climate Change (IPCC) reported that 17.3% of CO2 emissions in 2004 were the result of changing land cover, predominantly deforestation.
"Satellite imaging is helping to measure the rate and location of deforestation and contributing to scientific models that will improve our understanding of climate change."
In Borneo, Indonesia, the satellite constellation monitors tropical forest fires
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