- a 100% duty cycle option is already possible for the NIR detectors with some work, but no major software changes required. This is achieved by performing the pixel reset within the 10 µs frame read time. The settling time is 8 µs, then read & reset within the last 2 µs. This gives a duty cycle of 50% if a bias read is required, or 100% without the bias read is if a superbias is available. The superbias method would allow ngroups = 1, btu there's no reason we cannot use it for longer integrations.
- implementing such a mode requires editing the "personality file" in the ASIC (at Goddard)
- This read mode has no negative impact on non-TSO data.
- for MIRI the situation is more complex: the high-efficiency mode (the current FAST mode, without extra reset between integrations) is good for TSOs, but has very clear downsides for any observations that require absolute calibration (i.e. everything else). This is why the FASTR1 mode is being implemented.
- A superbias is much harder with MIRI as the zero point of the integration is much more flexible than in the NIR. The new extra reset mode improves a lot of systematics, especially the odd-even flux-dependent gain variations in the flat.
- It is also harder to switch back for MIRI, as Mike Ressler has optimised the bias voltages for the new readout mode and it is not trivial to switch back and forth.