I have been asked this question numerous times by many aspirants. Being tired of iterating the same time and again, I thought of sharing my experience with you.
As many times I have been asked the same, I can bet that I could never satisfy anybody with my reply. To my belief, no special preparation is required to crack the test. Anyone with a decent knowledge of Computer Science and an average preparation, can pass through the filters. At least it is true for exams conducted in the years of 2007, 2008, 2009, 2010. Now, “decent” and “average” are quite qualitative terms. Let me try to explain what I mean.
I wrote ISRO entrance exam. for the recruitment of Scientist/Engineer-‘SC’ on April 14, 2010. The advertisement came out in the month of February. I was working in TCS at that time. The project which I was working in was under extreme stress. Hardly a day passed when I did not have to work for extra hours. Almost eight months lapsed after I passed out B.Tech. It was that time only I “started” thinking to prepare for GATE. As you can understand, the situation was not at all favorable. What I could only do was to practice CS2007, CS2008 and CS2009 question papers available in their website. The exam pattern was like 1.5 hrs., 80 questions, 3 marks each. No calculator was allowed. The questions were not that difficult either. Just take a note that, only “real” challenge in it was the time factor. The time is half of that in GATE and number of questions were more than that in the same. Later on, I discovered that few questions were from previous years’ CS/IT GATE question papers itself.
Result came out. I was shortlisted for interview with an AIR 91. Adiyar ISRO guest house, Antariksh Bhavan, Chennai was my interview center. I was with the same company this time, too. Work pressure was a bit humanly at that time. Yet it was not at all comparable with a regular candidate. To cut the long story short, I appeared in front of the panel consisting of 7-8 members. They asked me questions from all the major topics in CS including Operating System, Networking, Data Structure, Software Engineering etc. It duration was about half an hour. I could answer most of the questions. But I was not confident. After all, it’s relative performance what matters. The next day, I left Chennai with a throbbing heart.
Time for the final result. They published it in the last week of November announcing me as AIR 11 out of 23 candidates selected in total. Joining date was March 16, 2012 at Vikram Sarabhai Research Centre (VSSC), ISRO.
Here is a collection of results for all branches for the recruitment in 2011.
Hope the information helps.