| BIT | Contents |
|---|---|
| 1 | AV3 corrected for ringing The value of AV3, the tap to the positive side of the V-axis coarse postion, was corrected for the effects of amplifier ringing during the event position calculations. For more information see Improving Chandra High Resolution Camera event positions via corrections to crossed-grid charge detector signals |
| 2 | AU3 corrected for ringing Similar to Bit-1 but for the U-axis |
| 3 | Event impacted by prior event (in development) This event occurred too close in position and time to a prior event. For more information see: "Pile-up" Effect on the HRC PSF |
| 4 | -- SPARE -- |
| 5 | Shifted event time The instrument was identified to be in a configuration that allows for high-precision timing. The event time has been taken from the value telemetered with the event that followed this one. For more information see HRC Event Time Tag Investigation |
| 6 | Event telemetered in NIL mode The event was telemetered while the HRC had low-bandwidth telemetry. The event times are unreliable. |
| 7 | V axis not triggered No tap on the V-axis had a signal that exceeded the coarse position determination logic. The event position is essentially unknown. |
| 8 | U axis not triggered Similar to Bit-7 but for the U-axis |
| 9 | V axis center blank event The event occurred outside of the bounds specified by the V-axis coarse position limits of the "blanking" function |
| 10 | U axis center blank event Similar to Bit-9 but for U-axis |
| 11 | V axis width exceeded The number of taps on the V-axis whose signals exceeded the trigger threshold is greater than an commanded value. Prior to 2000 Oct 5 the width threshold was 3 and this bit could be used to identify non-X-ray-background event. After that date the threshold was changed to 2 which will aid in identifying events that require a "ringing" correction. |
| 12 | U axis width exceeded Similar to Bit-11 but for the U-axis |
| 13 | Shield PMT active The MCP event occurred in coincidence with a signal from the anticoincidence shield PMT. This event is possibly due to a high energy particle. |
| 14 | -- SPARE (from hardware) -- |
| 15 | Upper level discriminator exceeded The size of the signal from the MCP exceeded the upper-level discriminator. The event may be due to a particle but may just be from the high end of the pulse-height distribution of X-ray events |
| 16 | Lower level discriminator not exceeded The size of the signal from the MCP did not exceed the lower-level discriminator. A small signal which may not have generated enough charge for a good position determination. |
| 17 | Event in bad region The event occurred in a region that has been identified as "bad" for one reason or another (hot-spot, dead-spot, no photocathode coating, ...) |
| 18 | Amp total on V or U = 0 The sum of the three tap signals on either axis that are used to determine the event position relative to the coarse position is zero. It is not possible to determine a valid event position and the event is placed at the center of the tap along the axis. |
| 19 | Incorrect V center The center tap (the one associated the the CRSV location) of the three taps on the V-axis is not the largest one (AV1 or AV3 > AV2). The reported V-axis coarse position is incorrect and the calculated event position is unreliable. |
| 20 | Incorrect U center Similar to Bit-19 but for the U-axis (AU1 or AU3 > AU2). |
| 21 | PHA ratio test failed The ratio between the sum of all six position taps, scaled for the relative gains and the switchable gains (AMP_SF), and the PHA (determined from the total charge striking the position grid) do not reflect the same signal size. The event is likely to be due to a particle. |
| 22 | Sum of 6 taps = 0 The sum of the signals from all six taps is zero. The event position is unknown but is placed at the center of the coarse positions reported. |
| 23 | Grid ratio test failed A comparison of the sum of the values of the three U-axis taps to the sum of the three V-axis taps is sufficiently different from 1.0 that the event position is thought to be unreliable. |
| 24 | ADC sum on V or U = 0 Same as Bit-18 |
| 25 | PI exceeding 255 The PI value (gain-uniformity corrected PHA) is larger than 255. |
| 26 | Event time tag is out of sequence The telemetered event time-tagging information is not consistent with a normal time sequence. This may be caused by a hardware sequencing issue (see Out-of-sequence HRC Time Tags) or it may be an indication of corrupted data. |
| 27 | V amp flatness test failed The relative distribution of charge between the taps on the V-axis is flatter than expected for an X-ray generated event. The event is likey to be due to a particle interaction. |
| 28 | U amp flatness test failed Similar to Bit-27 but for the U-axis. |
| 29 | V amp saturation test failed One or more of the tap signals on the V-axis exceeded their saturation level. The V-axis postion calculated for the event is unreliable. |
| 30 | U amp saturation test failed Similar to Bit-29 but for the U-axis. |
| 31 | V Hyperbolic-test failed The relative sizes of the tap siganls are such that they lie outside the bounds of a hyperbolic region in B versus (C-A) space, where A, B, and C are the negative-side, center, and positive-side tap signals normalized by the sum A+B+C. The hyperbolic region follows the observed locus points from X-ray events with reliable positions. |
| 32 | U Hyperbolic-test failed Similar to Bit-31 but for the U-axis. |