the present invention these include a simple single louver a series of folding louvers accordion type devices linearly sliding devices rotating sliding devices and other arrangements micro electro mechanical mems louvers of the present invention are similar to miniature venetian blinds that can be opened or closed to expose an underlying thermal control coating the mems louvers of the present invention open close to expose hide an underlying surface the louvers 39 outer surface preferably has a low emissivity while the underlying surface has a high emissivity the opposite approach is also clearly possible many thousands of miniature louvers each being hundreds of microns on a side would preferably be used some or all of the louvers could be fully or partially opened to achieve the desired variable emissivity effect it is also be possible to use this mems louver concept to vary effective absorptivity in a manner analogous to that described for emissivity variation fig1 a 1 b 2 a 2 b 3 a and 3 b show three embodiments of the mems louvers of the present invention fig1 a and 1 b show a simple single louver 10 of the present invention fig1 a shows the simple single louver 10 of the present invention in an open position while fig1 b shows the.