Unlike the "Deep Impact" probe, which by design struck comet Tempel 1's nucleus on 4 July 2005, "Philae" is not an impactor. Some of the instruments on the lander were used for the first time as autonomous systems during the Mars flyby on 25 February 2007. CIVA, one of the camera systems, returned some images while the "Rosetta" instruments were powered down, while ROMAP took measurements of the Martian magnetosphere. Most of the other instruments need contact with the surface for analysis and stayed offline during the flyby. An optimistic estimate of mission length following touchdown was "four to five months". The goals of the scientific mission have been summarized as follows: "The scientific goals of its experiments focus on elemental, isotopic, molecular and mineralogical composition of the cometary material, the characterization of physical properties of the surface and subsurface material, the large-scale structure and the magnetic and plasma environment of the nucleus. In particular, surface and sub-surface samples will be acquired and sequentially analyzed by a suite of instruments. Measurements will be performed primarily during descent and along the first five days following touch-down." "Philae" remained attached to the "Rosetta" spacecraft after rendezvousing with Churyumov–Gerasimenko on 6 August 2014. On 15 September 2014, ESA announced "Site J" on the smaller lobe of the comet as the lander's destination. Following an ESA public contest in October 2014, Site J was renamed "Agilkia" in honour of Agilkia Island. A series of four Go/NoGo checks were performed on 11–12 November 2014. One of the final tests before detachment from "Rosetta" showed that the lander's cold-gas thruster was not working correctly, but the "Go" was given anyway, as it could not be repaired. "Philae" detached from "Rosetta" on 12 November 2014 at 08:35 UTC SCET. "Philae" landing signal was received by Earth communication stations at 16:03 UTC after a 28-minute delay. Unknown to mission scientists at that time, the lander had bounced. It began performing scientific measurements while slowly moving away from the comet and coming back down, confusing the science team. Further analysis showed that it bounced twice. "Philae" first contact with the comet occurred at 15:34:04 UTC SCET. The probe rebounded off the comet's surface at and rose to an altitude of approximately .