Short answers, pulled from the story.
The standard temperature at a base geopotential altitude of zero meters below sea level is 19 degrees Celsius. This value serves as the starting point for all calculations within the model.
The tropospheric tabulation continues up to 11 kilometers where the temperature falls to minus 56.5 degrees Celsius. The stratospheric section extends from that boundary to 20 kilometers with constant temperature before a second layer begins.
The U.S. Committee on Extension to the Standard Atmosphere first published a model based on existing international standards in 1958. That initial version received updates in 1962, 1966, and finally 1976.
The International Organization for Standardization publishes the ISA as an international standard designated ISO 2533:1975. Other organizations like the International Civil Aviation Organization also publish extensions under their own authority.
At this peak height, temperature plummets to minus 86.204 degrees Celsius while density reaches 0.0014 kilograms per cubic meter at the stratopause below it. The mesosphere begins at 51 kilometers and extends upward to 71 kilometers before reaching this final layer.