Since 1978, long-term variations in the total solar irradiance have been monitored using spacecraft radiometers, at the 0.01 percent precision level. The irradiance measurements were performed from the Earth Radiation Budget Satellite (ERBS), Nimbus-7, Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), European Retrievable Carrier, Solar and Heliospheric Observatory (SOHO), and the Space Shuttle Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft platforms. Radiometer response can drift or shift at precision levels of a few hundreds of a percent. In-flight calibration sources are not available to detect radiometer response changes at radiometric accuracy or precision instrumental drifts or shifts which may be incorrectly interpreted as solar irradiance changes while consistent trends among the different measurements sets wee used to detect long-term irradiance variability components. In this paper, 1991-1998 corresponding ERBS, UARS, SOHO, and ATLAS irradiance measurements are inter-compared with each other as well as with the ERBS empirical irradiance fit. The empirical irradiance fit is based upon 10.7-cm solar radio flux and photometric sunspot index, indices of solar magnetic activity. Analyses of recent data sets identified no long- term shifts and drifts in the ERBS, SOHO, or UARS data sets. The typical value of the total solar irradiance is approximately 1365 Watts per meter squared.