Earlier this year, retired Air Force General Scott Gration was said to be favoured for the position of Nasa administrator.

BBC: Obama names US space agency chief

So I've appointed a special envoy, a Major General Scott Gration, a very close friend of mine, was one of the top fighter pilots in our military, in our Armed Forces, and somebody who's also an expert on development issues.

WHITEHOUSE: Town Hall in Arnold, Missouri

At the same time, a variety of other mediators, including the Qataris and a new American special envoy to Sudan, Scott Gration, have been encouraging the disparate rebel groups to resolve their differences and form a more coherent negotiating body.

ECONOMIST: The crisis in Darfur

Scott Gration, a policy adviser to the campaign, received a call from Pentagon officials earlier in the week expressing concerns about the trip -- specifically because Obama was heading there on his campaign plane and campaign staff members would be accompanying him on the visit.

CNN: McCain camp pounces on Obama troop visit cancellation

Scott Gration, Barack Obama's energetic new special envoy to Sudan, believes that the best chance of peace for this divided country remains the Comprehensive Peace Agreement (CPA) signed in 2005 between the Islamist government in Khartoum, in the north of the country, and the former rebels of south Sudan, who are quite separate from the Darfuris, and had been fighting their northern masters for most of the past half-century.

ECONOMIST: Sudan and Darfur