May be testing their new uplink setup. They will uplink channels from new dish and then check it ok to use. In this if signal gone, by informing this they avoid over flow of call and get faith of user.
I agree with Sbhopale because today again their signal is gone for few seconds on same time when signals were gone earlier on 14-11-12 so it is possible that they are setting up new uplinking center.
or may be insat 4a is dying and they r doing maintanance to make it sustain. we all know insat 4a ia having power issues since 1 and a half years and its life has already been reduced