ACS (Advanced Camera for Surveys) Repair

Repairing one of Hubble's most important instruments

In 2006 I was called to investigate an anomaly with ACS, and we realized during the course of the investigation that the instrument was damaged and would not function again unless a repair was made.  A problem in the power supply caused a loss of the instrument, and we decided to repair the instrument in space by removing the cover and changing out some circuit boards.

A completely new set of imaging electronics was needed, and we used Rockwell's SIDECAR ASIC as the main readout electronics for the ACS detector.  My role on this project was to design the FPGA that interfaces the SIDECAR to the existing electronics on Hubble.  This item became internally known as the "Translator FPGA".

ACS in Cleanroom SSDIF
This was the ACS instrument before its launch.  This image shot in our large SSDIF cleanroom.  The red circle shows the location of the CCD Electronics Box (CEB) that we would replace by removing all its circuit boards and replace with a new module with new electronics.

Cutting the cover grid on ACS CEB
The first operation to access the CEB boards is to cut the grid that protects the cover of the box.  This was done with this innovative plate that fits over the grid, and has small screw-actuated cutters that cut the legs of the grid. These screws are rotated by the Pistol Grip Tool (PGT).  As the screws are turned, sharp cutters protrude to cut the grid.

New CEB for ACS.  The CEB-R
The new boards are packaged into this module called the Replacement CEB, or the CEB-R.  The angle missing from the top cover is to avoid a beam inside Hubble that may have interfered with the installation.

Removal of old CEB boards by astronaut in cleanroom
Photo of an astronaut practicing the removal of the old boards from the CEB.  Shot inside the SSDIF cleanroom on our High Fidelity Mechanical Simulator.

FPGAs on the CEB-R circuit boards that I developed
The two FPGAs that I designed and that translate the data from the SIDECAR to the Hubble computers is shown in this red circle.  The code was written in VHDL.

CEB-R installed into ACS by astronaut in training pool
This is Mike Massimino inside his training suit doing the install of the CEB-R.  This is shot inside the Neutral Bouyance Laboratory pool.

ACS-R team members in Building 29 GSFC
This is most of the ACS Repair team.  Photo shot in Building 29 at NASA/GSFC.

At the front of the Shuttle launch pad with ACS-R team members
After travel to the Kennedy Space Center, some members of the team stood in front of the launch pad to spell out:
A (me), C (Kathleen), S (Erin), -R (Kevin).

ACS board removal in space
The moment that the old ACS board was pulled out of the instrument.  Operation performed in space.
The repair was very successful, and most of ACS was restored to operation.

ACS first light
I had the privilege of being invited to the "First Light" event for the repaired ACS instrument.
This took place at the Space Telescope Science Institute.

ACS first light
Formerly embargoed first light image (taken 6/13/2009).

One interesting historical point is that the data interface from the SIDECAR into Hubble has some unused data slots.  I had the liberty of deciding what to put into these 'fill' locations.  Taking an idea from a previous project, I decided to fill with the hex data byte "EC", which is 236 (decimal).  This is of course my initials.  As documented in the CEB-R Translator FPGA Design Description Document (HST-SW-010269), it causes ACS to periodically send my name into the Hubble Science Data Handling Computer, and then down to the ground data handling computers.

Spare bits are sent as EC
Excerpt from the Translator FPGA Description Document.


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