According to ISRO chief Madhavan Nair, Chandryaan's star sensor failed a month ago. Now the scientists are relying on the onboard gyroscopes and ground antenna to navigate the satellite. When ISRO suddenly posted a press release in their website in May, there were speculations of something gone wrong with the mission. Now, we know the reason. It'll be interesting to see, for how long they can navigate the satellite like this, and how much more data it can collect. Good luck Chandrayaan!