1. Vikram Sarabhai Space Centre, Indian Space Research Organization, Thiruvananthapuram, IN (Corresponding author), e-mail: ramesh_narayanan@vssc.gov.in; rameshnarayananp@yahoo.co.in
2. Dept. of Materials Engineering, Indian Inst. of Science, Bangalore, IN
3. Vikram Sarabhai Space Centre, Indian Space Research Organization, Thiruvananthapuram, IN