Based on data gathered during focus measurement programs 8977 and 8980 ( both part of the Servicing Mission On-orbit Verification (SMOV) schedule), the NICMOS focus in all three cameras has been measured. Continuing monitoring data from Cycle 11 monitoring programs 9323 and 9637 as well as Cycle 12 program 9994, have shown the focus to be stable. Changes in the optimal positions of the Pupil Alignment Mechanism (PAM) for NIC1, NIC2 and NIC3 have been made to reflect those measurements. The optimal focii are similar to those observed in Cycle 7, however both the NIC1 and NIC2 focii have moved slightly in the negative direction (bringing them closer to 0) and the NIC3 focus has moved slightly in the positive direction, bringing it closer to being in-focus. As you may recall, NIC3 has always been out of focus due to deformations in the optical bench. Please refer to the History of the NICMOS Focus through 1999 for more details on the history of the NICMOS focus.
The post-NCS focus measurements have revealed very good stability. The focus monitor measurements are listed here in tabularform as well as in a focus history plot. Additionally, the individual post-NCS focus histories for each of the cameras has been plotted along with the Cycle 7 and 7N focus measurements as a comparison. The pdf plots for NIC1 focus history, NIC2 focus history, and NIC3 focus history, can be seen here. Slight variations in the focus position are due to short term (orbital) and long term (monthly) variations in the hst optics, as well as an HST secondary mirror move which took place on December 3, 2002. This phenomenon, know as breathing, is not corrected for in these results due to the lack of a robust breathing model for the NICMOS optics. You can find all details of the NICMOS focus on the Focus page of this website.