Wake vacuum measurement and analysis for the wake shield facility free flying platform

We report here the temperature and pressure measurements recorded on the Wa ke Shield Facility (WSF) during the two flights in which it was a free flye r in low earth orbit. The WSF is a disk-shaped platform on which are attach ed, on the wake side, apparatus necessary for the epitaxial growth of thin film materials. Previous calculations suggest that the pressure on the wake side could be decreased by some 6 orders of magnitude over the ambient pre ssure in low earth orbit (from 10(-8) to 10(-14)Torr). Analysis of the pres sure and temperature data gathered from the two flights and presented here concludes that the decrease was some 2 orders of magnitude or 4 orders of m agnitude less than expected. Reasons for this discrepancy are proposed and it is suggested that the original pressure values could be reached if, prio r to growth, the WSF was sufficiently outgassed. (C) 2001 Elsevier Science Ltd. All rights reserved.