Hello Mert,
You need to specify, what calibration (for which chunk and which sensor) you need to save, for example, the following code saves the calibration information for the first sensor (calibration group) of the active chunk:
import PhotoScan
calibration = PhotoScan.app.document.chunk.sensors[0].calibration
calibration.save("C:\\Users\\MERT\\Desktop\\Belgeler\\Staj\\İHA Proje\\U1\\ddd.txt",format='australis')
For Australis format export you may need to use pixel_size argument:
pixel_size = PhotoScan.app.document.chunk.sensors[0].pixel_size