Altitude control and three axis stabilization of the solar sail is critically important and may be accomplished either through a mechanical arrangement or through the use of variable solar reflectance/transmittance coatings (VSRCs/VSTCs). Electrochromic coatings that change reflectance or transmittance in response to the application of an electric potential may be used for this purpose. The primary objective of this work is to evaluate the effect of changes in the emittance of the front and rear surfaces of a solar sail on the thrust modulation efficiency. The results presented in this article demonstrate that the most efficient change in thrust for a solar sail panel with a VSRC is reached when the side shaded from the sun has the higher emittance than the side facing the sun. For a solar sail panel with a VSTC, the condition for the most efficient change in thrust occurs when the side facing the sun has the higher emittance than the side shaded from the sun. Also, it was highlighted that an opaque VSRC is more compatible with an opaque reflective solar sail thruster than a transparent VSTC. This design of a solar sail altitude control system with VSRC panels is recommended for further development. © 2004 American Institute of Physics