High-resolution accelerometers and gradiometers on board of drag-free satellites are employed in different scientific space missions. The applications range from experiences in fundamental physics to the earth's observations associated with the precise orbit determination of low earth's orbiter (LEO) particularly in context with the autonomous navigation and the determination of the short wavelength part of the earth's gravity field which is an important topic of satellite Geodesy. A satellite flying drag-free, which means that all non-gravitational conservative forces exerting on the satellite are compensated by a drag-free control (DFC) system, is best suitable to achieve the mission goals of these applications. In addition to proportional thrusters for the compensation of the conservative forces, a DFC system can comprise electrostatic space accelerometers, which also constitute a gradiometer, in order to measure the corresponding non-gravitational forces with very high sensitivity (i.e. better than 1 pg). As an input for a DFC system, an accelerometer signal can be limited by so called internal parasitic forces which are inherent to the physics of the system and are applied directly to the proof mass of the accelerometer. This paper presents thermodynamical foundations of two essential thermodynamical parasitic forces acting on the proof mass of the accelerometer and gives an estimation of their magnitude. Additionally, orbit predictions for 5 days are performed with and without thermodynamical disturbances to estimate possible trajectory errors of a drag-free satellite. (C) 2003 Elsevier B.V. All rights reserved.