<title>Optical properties of water released in low earth orbit</title>

Abstract

A D --266 9 '1 kG I0MSNyo, 0704-0 188iii c G ~the lime for rqv,*t.g ifftuuuvorn. searchmf esiIMnq data I0 =7gg a n manc l IIlIIIIIII Swll rend fll falmmitili egrding thi ,rden estimate of any~ Othtr asetOf hi 0-% "K&V 9nOm lllili .i 11111II111li l souner $r,.Oi r ota Ic lot inflion 00 oraoris and Repoili. 9 i AGENCY USE ONLY (Ledvi 93-14691Analysis of intensified video photographs of a twilight venting Of excess water from space shuttle showed that the -1 mm diameter stream cavitasionally fragments within about 1 =. forming two discrete-Particle components and vaOor. The images from nearby cameras are domitiated by irregular, polydisverse water/ice droplets with sizes comparable with the venting orifice and outward velocity indistiguishable from that of the initially coherent Liquid. In contrs-st the 2VA lzz-loog quasconical mril imaged from a distant ground station consists of 1cc opaflyifl submicroO ice spberules that were produc-Ed by partial recoodensation of the overexpanded vacuum-evaporatted water gas, which are sublimating at rates that we calculated from the measured faloff of aial sunlight-scatter radiance and the energy balance of progressively roughening ice at 329 Ian altiude-, at low latitudes they cool to 180K in < 1 s. 2nd their radii transition to the Rayleigh-SCa2tttrilg range in LMi The very much larger fragmentation particles come to a slightly higher equiLibrium temperature within -2 min, and persist for a few earth orbits. Thes three components of the vented water (and other high vapor pressure liquids) radiate and scatter earthshine and solar photons. and tne orbital-velocity molecules are also excited by collisions with the residual atmlospheric gas, overlaying wide-angle conaminating foregrounds On remotc Optical sensing from onboard. The particle sizes, diensities, and tEmpes-anres derived from the visible data are applied in eswtin~fg ultraviolet and iafrared radiances of the icei'vapor-containing volumes near Shuttle Orbiter. SUBJECT TERMS NUMBER OF PAGES Optical properties Orbital-velocity molecules 12Low Rarth orbit Solar photons PL-TR-93-2134Optical properties of water released in low earth orbit ABSTR-CrAnalysis of intensified video photographs of a twilight venting of excess water from space shuttle showed that the -1 mm diameter stream cavitationally fragments within about I 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'h ki-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 kim altitude; at low latitudes they co...

Conference Report: Workshop on Water - Its Measurement and Control in Vacuum - Gaithersburg, Md - May 23-25, 1994

“…Although the presence of water vapor is known to affect the performance of space sensors, quantification of the amount and sources of water contamination are not well understood. A future experiment, the MSX spacecraft mission [ 8 ], will include a suite of sensors to accurately measure the local environment surrounding the spacecraft as a function of time in orbit. The experiment is expected to determine the necessary time in orbit required for proper water degassing before optical sensors are activated and will also assess the effectiveness of current ground contamination control procedures.…”