Optical Properties of Water Released in Low Earth Orbit
Abstract
Analysis of intensified video photographs of a twilight venting of excess water from space shuttle showed that the approx. 1 mm diameter stream cavitationally fragments within about 1 m, forming two discrete-particle components and vapor. The images from nearby cameras are dominated by irregular, polydisperse water/ice droplets with sizes comparable with the venting orifice and outward velocity indistinguishable from that of the initially coherent liquid. In contrast the 2 1/2 km-long quasiconical trail imaged from a distant ground station consists of accompanying submicron ice spherules that were produced by partial recondensation of the overexpanded vacuum-evaporated water gas, which are sublimating at rates that we calculated from the measured falloff of axial sunlight-scatter radiance and the energy balance of progressively roughening ice at 329 km altitude; at low latitudes they cool to 180K in < 1 s, and their radii transition to the Rayleigh-scattering range in approx. 1 min. The very much larger fragmentation particles come to a slightly higher equilibrium temperature within approx. 2 min, and persist for a few earth orbits. These three components of the vented water (and other high vapor pressure liquids) radiate and scatter earthshine and solar photons, and the orbital-velocity molecules are also excited by collisions with the residual atmospheric gas, overlaying wide-angle contaminating foregrounds on remote optical sensing from onboard.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 21, 1993
- Accession Number
- ADA266197
Entities
People
- Christian A. Trowbridge
- David L. Rall
- Irving L. Kofsky
- James A. Gardner Ii
- Rodney A. Viereck