with sticky relays, a procedure that required the complete electrical power down of the spacecraft for the first time since it was launched.[72][edit] Servicing Mission 4Main article: STS-125Wikinews has related news: NASA launches Space Shuttle AtlantisAstronauts work on Hubble during SM4Hubble floats free from Atlantis after SM4.Servicing Mission 4 (SM4), which took place in May 2009, was the last scheduled shuttle mission (STS-125) for the Hubble Space Telescope.[73] The mission was first planned for October 14, 2008.[74] However on September 27, 2008, the Science Instrument Command and Data Handling (SI C&DH) unit on HST failed. All science data pass through this unit before they can be transmitted to Earth. Although it had a backup unit, if the backup were to fail, the HST's useful life would be over.[75] Therefore on September 29, 2008, NASA announced that the launch of SM4 would be postponed until 2009 so the SI C&DH unit could be replaced as well.[76] SM4, with a replacement SI C&DH unit,[77] was launched aboard Space Shuttle Atlantis on May 11, 2009.[78]On SM4, astronauts, over the course of five spacewalks, installed two new instruments, Wide Field Camera 3 (WFC3), and the Cosmic Origins Spectrograph (COS). WFC3 will increase Hubble's observational capabilities in the ultraviolet and visible spectral ranges by up to 35 times due to its higher sensitivity and wider field of view. The telephone-booth sized COS assembly replaced the Corrective Optics Space Telescope Axial Replacement (COSTAR) that was installed in 1993 to correct Hubble's spherical aberration problems. (COSTAR was no longer needed after the replacement of the FOC in 2002, the last original instrument without the necessary correction built in.[65]) The COS will do observations in the ultraviolet parts of the spectrum, complementing the measurements done by the repaired STIS system.The mission repaired two instruments that had failed, the Advanced Camera for Surveys (ACS) and the Space Telescope Imaging Spectrograph (STIS). The astronauts also performed other component replacements, including all three Rate Sensor Units (each containing two gas-bearing gyroscopes); one of three Fine Guidance Sensor (FGS) units used to help keep pointing accuracy and increase platform stability; the SI C&DH unit; all six of the 125-pound (57 kg) nickel-hydrogen batteries used to provide all Hubble's electrical power to support operations during the night portion of its orbit; and three New Outer Blanket Layer (NOBL) thermal insulation protective blankets. The batteries had never been replaced and were more than 13 years over their original design life.[79]Atlantis released the Hubble Space Telescope on May 19, 2009 back into space after all repairs were successfully made. After testing and calibration, Hubble resumed routine operation in September 2009.[80] These efforts are expected to keep the telescope fully functioning at least into 2014, and perhaps longer.[81]Hubble was originally designed to be returned to earth on board a shuttle. With the retirement of the shuttle fleet, in July 2011, this is no longer possible. NASA engineers developed the Soft Capture and Rendezvous System (SCRS), a ring-like device that was attached to Hubbles aft bulkhead during SM4, which will enable the future rendezvous, capture, and safe disposal of