Scientists Say Goodbye to Philae Comet Lander (cnn.com)
Today, scientists from the German Aerospace Center (DLR) announced that they are saying goodbye to Philae, the comet lander that is currently perched on Comet 67P/Churyumov-Gerasimenko as it races toward the sun. According to Stephan Ulamec, Philae's project manager, "Unfortunately, the probability of Philae re-establishing contact with our team at the DLR Lander Control Center is almost zero." Philae first made history when it successfully landed on a comet in fall of 2014, but problems soon began when commands were not able to reach the robot.
If I recall, when the lander hit the comet it was supposed to fire spikes or other anchors into the comet to hold in down, but one or more of them didn't fire and so the lander bounced around a lot and ended up under a shaded cliff. Yes, the whole program was great and can very well be considered successful, but it didn't work exactly as intended.