Only seven degrees south of the equator, a full moon overhead illuminates the beach, seemingly brighter than at home in South Africa. It's two hours to midnight and we stroll in shorts and T-shirts in the balmy night.

We have travelled by ship 2400 miles north of Cape Town to the island of Ascension, a tiny speck in the middle of the Atlantic Ocean midway between Africa and South America.

The first human contact with Ascension Island proved something of a mis-conception. Click here, to find out why this volcanic outcrop in the Atlantic Ocean is called Ascension, and not Conception Island.

We scan the beach looking for telltale turtle tracks. It's late in the breeding season, which peaks in the months from January to May. We have come all this way hoping for a meeting. The turtles, like us, will have undertaken a long sea journey, migrating 1000 miles from the South American coast. All is expectation.

The conical-shaped depressions in the sand are evidence that Long Beach in Clarence Bay, along with the other sandy beaches on the island, is a major breeding place for the Green turtle (chelonia mydas).

Amy,9, and Olivia,7, my daughters, discover egg shells half-buried in the sand. Unlike other nesting sites in places such as Costa Rica, Suriname, Aves Island, US Virgin Island, Florida and Puerto Rico, the nesting colony on Ascension is relatively well-protected because of the military presence on Ascension and controlled access to the island.

We are the only people on the beach tonight, but mostly it is humans who have caused the extinction of green turtle populations, which once nested in Bermuda and the Cayman Islands. The Green turtle, once slaughtered by the hundreds, is considered the best eating of all the turtles, but as a consequence is now on the endangered species list.

We see a dark shape moving out of the sea. This is incredible, so late in the season! We sit on the sand 150 metres away and watch the turtle make laborious progress up the beach. I am taken by surprise. Should I dash the two kilometres back to the bungalow to fetch the cameras?

I know the nest-making process and egg-laying will take about two hours. I decide to risk fetching the camera.

I return breathless, but immediately see that my effort does not come close to that required of the turtle. She's hauled herself 500 metres up the white beach and has already moved about half a ton of sand using her front and rear flippers in a dextrous and well-co-ordinated movement. She rests between exertions and sighs.

Judging by her size, this turtle hen will be 40 to 50 years old and probably weighs 140 kg. There is a strong site-fidelity, so it is almost certain she hatched on this very same beach many years ago.

In geological terms Ascension Island is young: the oldest exposed rocks are a mere one million years old. Volcanic action has continued through to recent times, and geologists suggest that the "newest" flows took place in the last 1000 years, although there are no reports of eruptions since the island's discovery in 1501.

The children have fallen asleep by the time she begins to lay her clutch of 100 or so eggs. There is less chance of disturbing her now, so we creep closer.

On average, two to three clutches are deposited at two-week intervals, but usually two to four years intervene between an individual turtle hen's egg-laying, the females needing that time-frame to recuperate. Mating occurs in the water off the nesting beaches, and while it is not 100% proven, it would appear that the males migrate to the nesting beach every year.

Other than human predators such as the Lord Mayor of London, who in times past always had turtle soup on the menu for his annual banquet there are others like the frigate bird which takes young turtles running the gauntlet from the nest back to the sea.

Only one in 500 hatchlings will make it to adulthood. Somewhere deep in the species memory, the turtle we are watching seems to know the odds are stacked against her offspring. She covers her nest, with elegant flipper movements efficiently moving mounds of sand, and then disturbs and repacks another ton of sand, creating a decoy nest.

We sense it is time to wake the children. Olivia is tearful but is soon captivated, especially when we notice miniature tracks, first one, then dozens.

It seems the slight drop in temperature in the early morning hours has caused an eruption of young turtle hatchlings all making a dash to the sea at night, instinctively improving their chances of survival. We have to caution Amy, who wants to carry the little ones across the beach and down to the sea.

It's a hard lesson, standing by and allowing hundreds of thousands of years of evolution to naturally follow its course. I find myself wondering if Darwin experienced what we saw tonight when he visited the island in 1836. It is on record that he wrote about the island's geology, but was he graced by the gentle moonlight and the presence of turtles? Of course, I cannot know what he thought or felt, but if it were possible, I would wish him to know that - for us, tonight - the island is smiling.

Satellites and Lunar Vehicles:

The island of Ascension has always been a hub for communication activities. In the 17th and 18th Centuries, sailing ships would drop their mail under the "post-office" stone, to be picked up and delivered by ships sailing in the opposite direction.

More recently, Ascension was a major relay point of the co-axial submarine cable system laid between the United Kingdom, Portugal and South Africa with links to South America and West Africa.

This cable system no longer operates. Instead, Cable and Wireless operate an international satellite telecommunications service, and operate the "Ariane" Earth Station on the island on behalf of the European Space Agency. In 1967, the BBC opened its Atlantic Relay Station broadcasting to Africa and South America.

The Americans operate satellite tracking stations and other facilities, which include the southernmost USAF Eastern Missile Test Proving Ground. In 1966, Ascension became famous when NASA built a satellite earth station which was part of the Apollo project. Coincidentally the Lunar Rover was tested on the island, the volcanic terrain being thought to most closely approximate the lunar landscape. Apparently, several mid-Atlantic hydrophones (underwater microphones) monitor underwater traffic like submarines moving north and south past Ascension.

Non-military users of the GPS navigation system might not be aware that Ascension is one of five earth monitoring stations essential to the systems fuctioning. The five locations are Hawaii, Kwajalein, Ascension Island, Diego Garcia and Colorado Springs. In addition, there are three ground antennas at Ascension Island, Diego Garcia and Kwajalein, plus a master control station (MCS) located at Falcon airforce base in Colorado.

The monitor stations passively track all satellites in view, accumulating ranging data. This information is processed at the MCS to determine satellite orbits and to update each satellite's navigation message. Updated information is transmitted to each satellite via the ground antennas.