title: Simultaneous two-wavelength holographic interferometry in a superorbital expansion tube facility.
abstract: A new variation of holographic interferometry has been utilized to perform simultaneous two-wavelength measurements, allowing quantitative analysis of the heavy particle and electron densities in a superorbital facility. An air test gas accelerated to 12 km/s was passed over a cylindrical model, simulating reentry conditions encountered by a space vehicle on a superorbital mission. Laser beams with two different wavelengths have been overlapped, passed through the test section, and simultaneously recorded on a single holographic plate. Reconstruction of the hologram generated two separate interferograms at different angles from which the quantitative measurements were made. With this technique, a peak electron concentration of (5.5 +/- 0.5) x 10(23) m(-3) was found behind a bow shock on a cylinder.
authors.forename: T J
authors.initials: TJ
authors.lastname: McIntyre
authors.forename: M J
authors.initials: MJ
authors.lastname: Wegener
authors.forename: A I
authors.initials: AI
authors.lastname: Bishop
authors.forename: H
authors.initials: H
authors.lastname: Rubinsztein-Dunlop