A GUIDE TO THE USE OF MHER7
As noted in Express No. 11 p.3 MHER7 is a new OBC program, developed in response to the discovery of quasi-periodic oscillations from some X-ray binary sources, which provides high time resolution (sub-millisecond) intensity samples and an option of limited energy resolution for the ME experiment data.
MHER7 gives 4-bit intensity samples, summed over a selectable time interval in 1, 2 or 4 selectable energy ranges. The intensity is determined by counting valid events (E 0) within the specific energy and time range (defined as a number of samples of the E channel). Since 4-bit counters are used, the maximum counts/sample is 15 and the integration time should be selected to give a count rate/sample of significantly less than 15. This can be achieved quite simply by setting the integration period to 14 E channel samples ( 14 events, irrespective of input count rate). Energy ranges can be defined arbitrarily within the total spectral range from ADC channel 0 in Argon to ADC channel 127 in Xenon.
There is no selection according to detector ID and MHER7 is therefore more suited to co-aligned observations.
When configuring MHER7 care is necessary to avoid CPU overload (and the attendant problem of safety mode monitoring during an OBC 'crash' - ref. Express No.9 p.4) and TM overflow when discontinuous data would result. CPU overload errors are possible if MHER7 is running in conjunction with other CPU-intensive programs such as MHER5, or MHER4. A limit of 82% CPU usage is set by the operations team to ensure that such errors do not occur and this has the following implications:
Note that the normal sampling of the ME energy channel for use in MHER7 is 4k
s-1. In principle, 8k s-1 would be feasible although the non-experiment
sequencer samples (ref. Express No.5 p.38) at slots 1 and 257 would lead to
non-uniform dead times throughout the software cycle and difficulty in
interpretation of the data. Use of an 8k sample rate is therefore strongly