pixel images ($2.5^{\prime}$ on a side).

We began our analysis using event data calibrated by the initial processing and made available through the  public archive. The first observation revealed several problems in the standard data sets and further problems were subsequently found during the analysis of the second observation. These problems affected both the spatial and timing analyses and had significant implications for the proper interpretation of the data. We alerted the HRC hardware and software teams to the instrument and data processing anomalies, and received considerable support in working through the problems. We document here the various artifacts discovered and the steps taken to correct for, or eliminate, them in our final data sets; our goals in doing so are 1) to allow for the replication of our results, and 2) to alert other early HRC users to problems they may encounter. In fact, we found it necessary to reprocess the data from Level 0.5 using custom scripts which incorporated improved filtering and processing tools, making use of several beta versions of software provided by the HRC team.

In the first observation we found evidence for a significant “ghost image” which appeared as a spectacular jet-like feature emanating from 