[1] Natl Phys Lab, Teddington TW11 0LW, Middx, England
[2] UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England
[3] Far W Technol, Goleta, CA 93117 USA
[4] Civil Aviat Author, Gatwick RH6 0YR, W Sussex, England
[5] Virgin Atlantic Airways Ltd, Crawley RH10 2NU, W Sussex, England