This week on HST

HST Program: May 18 - May 24, 2009

Space Shuttle Atlantis launched at 2.01 pm EDT on Monday May 11th to carry out Servicing Mission 4 to the Hubble Space Telescope.

HST ceased Cycle 16 science observations at 0 hours UT on Tuesday May 12th (8 pm EDT), preparatory to orienting the telescope for rendezvous with Atlantis, which occured at 1 pm on May 13th. In the interim, the crew performned an extensive inspection of Atlantis for potential damage during launch, identifying a few nicks that were deemed sufficiently minor to not require further inspection. This conclusion cleared the way for all five EVAs to be devoted to Hubble instrument replacement and repair.

Cycle 16 formally started on July 1 2007 and terminated on May 11th 2009, a duration of 681 days.

The first EVA, conducted by John Grunsfeld and Andrew Feustel, with Megan McArthur operating the robot arm, took place on Thursday May 14th, and involved swapping out the venerable Wide-Field Planetary Camera 2 (WFPC2), installed in the first servicing mission, 16 years ago. WFPC2 didn't want to leave, but finally relented (much to everyone's relief), making way for the installation of Wide Field Camera 3. In addition, the new Science Instrument Command and Data Handling Unit (SIC&DH) was installed, replacing the unit that suffered a failure in one electronic channel late last year, pushing SM4 from October 2008 to May this year. Both WFC3 and the new SIC&DH have passed aliveness and functional tests. Largely as a result of WFPC2's recalcitrance, the EVA lasted 7 hours 20 minutes, 50 minutes longer than planned.

EVA 2 took place on Friday May 15th, with Mike Good and Mike Massimino assisted by Megan McArthur. All three Rate Sensor Units (gyros) were replaced, not without some drama as one of the new units refused to mate with two locations on the telescope. As a result, that new unit was set aside in favour of an older, refurbished unit. By that time, the EVA was almost 2 hours behind schedule, but the astronauts gave the go-ahead to continue, and the battery module in Bay 2 of HST was replaced with a new unit. Both battery units are originals, and the second unit will be replaced in EVA 5. The EVA lasted 7 hours 56 minutes, the 8th longest on record.


EVA 3 was completed on Saturday May 16th. Originally, the schedule included replacing COSTAR (the optical unit inserted in SM1 to correct spherical aberration) with the Cosmic Origins Spectrograph (COS), and the first part of the repair of the Advanced Camera for Surveys (ACS), which suffered an electronic failure that disabled the Wide Field and High Resolution Channels in January 2007. However, perhaps to make up for the first 2 EVAs, there were no unforeseen issues, and Grunsfeld and Feustel zipped ahead of schedule to the extent that they installed COS and completed the full ACS repair more than an hour ahead of schedule. The full EVA lasted 6 hours 35 minutes. Both COS and ACS passed the aliveness tests, and COS successfully completed the full sunctionality test. On ACS, the Wide Field Channel (ACS/WFC) was recovered and passed the initial functional tests, but the High resolution Channel was not recovered. This eventuality was not unexpected, and still leaves Hubble with four cameras: the UVIS and IR channels on WFC3, and the WFC and ultraviolet-sensitive Solar Blind Channel on ACS.


EVA 4 was scheduled for Sunday May 17th, and included repair of the Space Telescope Imaging Spectrograph (STIS). As with EVA 2, the repairs were conducted by the two Mikes, and, as with EVA 2, there were complications. In particular, a large handle (handhold) on STIS had to be removed to allow access to the cover plate; one of the securing bolt stripped, and it took 2 hours and, eventually, brute force to finally get it out of the way. Once the crew gained entry to STIS, the mini-power tool designed to remove the 111 STIS screws proved to have a dead battery, and had to be replaced with the spare. Once all that was out of the way, the repair went very smoothly. With all this extra work, the EVA lasted 8 hours and 2 minutes (6th longest ever). The initial aliveness tests for STIS were successful.


The fifth and final EVA took place on Monday May 18th. Grunsfeld and Fesustel installed the second replacement battery unit and replaced one of the Fine Guidance Sensors. They also installed several new sets of insulating material (the NOBLs, or New Outer Blanket Layers), including one set on Bay 8 that had to be delayed from EVA 4. In the final stages of the EVA, the Low-Gain Antenna was bumped, resulting in slight damage to the outer shell. There are no functional problems with the antenna, but a cover was installed to ensure that there was no thermal damage.

HST was released from Atlantis at 08:57 EDT on Tuesday May 19th. Atlantis is scheduled to land at Kennedy at 10:00 am on Friday May 22nd.

In the succeeding weeks, the new (and refurbished) instrumentation on HST will undergo an extensive series of tests as part of the Science Mission Orbital Verification (SMOV) process. HST will remain pointed away from the Earth until mid-June; the materials in the new instruments and add-ons undergo outgassing, which, under bright illumination, can lead to contamination that can reduce the UV throughput of optics. The instruments are then brought on-line in order, starting with the ACS/SBC in late-May and ending with COS in August. The first scientific results and new images from Hubble, the Early Release Observations (EROs), will not be available until later in the year.

Science observations will resume in late summer, as Cycle 17 programs are gradually phased in towards the end of the SMOV process.

Selected highlights

Atlantis launches from Kennedy Space Center en route to HST

One of the sold rocket boosters from Atlantis splashes down into the Atlantic, for later recovery.

Rendezvous: Atlantis and HST silhouetted against the Sun

The official EVA schedule

Atlantis captures HST

Astronauts John Grunsfeld and Andrew Feustel install WFC3 on the first EVA

Grunsfeld and Feustel deal with COS and ACS on EVA 3

Astronauts Mike Massimino and Mike Good deal with the recalcitrant STIS handle on EVA 4

John Grunsfeld on the final EVA

Hubble is deployed from Atlantis following the completion of SM4