To update the firmware on a Spirent GNSS simulator then the following documents apply. The latest firmware files are available for download, for supported customers, from the Spirent Support Website (the exception to this rule is for STR47xx series simulators which require a physical PROM to be supplied by Spirent - contact Spirent Applications Support for further information).
For GSS4100 / 4150 / 4200 / 4500 / 5060 / 6100 / 6560 simulators, follow DCS0032A
For STR4730 / 4750 / 4760 / 4780 / 4790 simulators, follow DCS0029A
For GSS7700 / 7730 / 7735 / 7790 / 7800 / 7900 and GSS8000 simulators, follow DCS0030A
For the GSS6300 and GSS6700 simualtors, follow DCS0038A