I don't know how different are the work environment of ISRO and DRDO but I guess it must be same. One of my colleague at Tata Consultancy Services, an ABAP developer, left his job with decent salary and an opportunity to go to UK for an offshore project of 2 years. Why? To join DRDO at salary 4 times less than what he was getting coz he hated his work and was passionate about working on something that is not just interesting but also makes a difference.