SIV meaning in Space Science ?

A sieve, fine mesh strainer, or sift, is a device for separating wanted elements from unwanted material or for characterizing the particle size distribution of a sample, using a screen such as a woven mesh or net or perforated sheet material. The word "sift" derives from "sieve".

In cooking, a sifter is used to separate and break up clumps in dry ingredients such as flour, as well as to aerate and combine them. A strainer (see Colander), meanwhile, is a form of sieve used to separate suspended solids from a liquid by filtration.