What is the ideal time for remote sensing, and why?

Answer 1

The simple, and thoroughly unhelpful, answer: it depends on what data you are after and what you intend to do with it.

In general, if you are after data connected with the surface (e.g., optical imagery of impervious surfaces, optical or spectral signatures of soil, etc.) you want to collect the data during late fall or early to mid-spring. This should coincide with deciduous vegetation being bare and avoid the ground being obscured by snow. Unfortunately, obtaining useful optical imagery during this time can be difficult due to heavy cloud cover. Alternatively, if what you are looking for is data relating to vegetation health, productivity, canopy cover and density, etc. the leaf-on season (usually the mid- to late summer) would be the ideal time. If, however, you were looking to collect data pertaining to something more transient such as assessing and monitoring water quality or temperature such you should collect data at multiple throughout the year(s).

The key to optimizing remote sensing technology and data is to understand both remote sensing and the subject it is being used to study.