Mode = ALIGN Config = WFC3/UVIS or WFC3/IR

This Mode is used to move the WFC3 internal focus and tilt mechanisms for the UVIS or IR channel (depending on the selected configuration) via stored commanding for the purpose of on-orbit alignment of the aberration correction optics. ALIGN exposures do not acquire science data and must be interleaved with science mode exposures to obtain data, with the alignment mechanisms at a variety of positions for the ground alignment process.

The proposer must ensure that the alignment scans are within the allowed mechanism limits. The mechanism positions, corresponding to the nominal zero positions of the alignment scan, will be set via real-time command. This will be accomplished in a proposal by specifying an ALIGN mode exposure with the special requirement REQuires UPLINK. Because the positions of the mechanisms are set via real-time command, optional parameters are disallowed in conjunction with the REQuires UPLINK special requirement to prevent commanding the mechanisms via stored commands.

Any visit which contains ALIGN mode exposures must use a single configuration for all exposures (including the science exposures), either WFC3/UVIS or WFC3/IR but not both. The use of internal targets (other than NONE) in visits containing Mode=ALIGN exposures is not allowed. A WFC3/IR visit must contain an external target exposure.

Target Name

The special value NONE must be specified.

Aperture or FOV

Do not enter a value.

Spectral Element

Do not enter a value.

Wavelength

Do not enter a value.

Optional Parameters

FOCUS

= 0 (default); -11232 to +11232 (steps)

Specifies the relative position from a nominal zero position of the focus mechanism, in motor steps. The absolute position of the nominal zero is set by real-time command.

TILT

= NO (default), YES

Specifies whether a tilt of the corrector mechanisms will be commanded. If this parameter is set to YES, the maximum time required to move both cylinders of the tilt mechanism will be included in the alignment time. You should consult with the Commanding Team regarding QESIPARM and QELOGSHEET special requirements needed to specify the tilt scan.

Number of Iterations

The Number_Of_Iterations must be 1.

Time Per Exposure

Proposers may specify a positive value of Time_Per_Exposure to provide for additional time after the move has completed to wait prior to the start of the subsequent WFC3 exposure. This time may be desirable if, for instance, the corrector move in the ALIGN Mode exposure could adversely affect the thermal environment (due to running the motors) and a cool-down time is required before the science exposure.

Special Requirements

Optional  parameters  may  not  be  specified  for  ALIGN  exposures  with  the

REQuires UPLINK special requirement.

Mode = ANNEAL Config = WFC3

This Mode allows specification of periods of time during which the WFC3 will be warmed for hot pixel repair. The total annealing time will be the specified exposure time plus a minimum, default value (12 hours). The ANNEAL exposures do not collect science data. The Anneal exposure must be in its own visit due to the time required to configure the instrument for the procedure.

Target Name

The special value NONE must be specified.

Aperture or FOV

Do not enter a value.

Spectral Element

Do not enter a value.

Wavelength

Do not enter a value.

Optional Parameters

IRTEMP

= COLD, WARM

This parameter must be specified.

No WFC3 science can be scheduled during an IRTEMP=WARM, anneal. WFC3 IR science can be scheduled during an IRTEMP=COLD anneal (see Time Per Exposure).

Number of Iterations

The Number_Of_Iterations must be 1.

Time Per Exposure

The STScI ground system enforces a minimum anneal time of 12 hours. If a longer time is needed, specify a total time that includes this 12 hour minimum.

• Any value less than 12 hours (43200 seconds) will result in a 12 hour anneal.
• Any value greater than 0 will prevent IR science from scheduling during the initial specified portion of an IRTEMP=COLD anneal. Therefore, specify a Time_Per_Exposure = 0 for a nominal 12 hour IRTEMP=COLD anneal during which parallel IR is permitted.

Special Requirements

SAA CONTOUR defaults to model 11 (non-intersecting). The ANNEAL exposure only triggers the reconfigurations that actually perform the anneal process so this potentially long exposure does not have to avoid the SAA. Using any other model may result in inefficient scheduling with the potential for the detectors to be left in unusual states longer than necessary. Changing to something other than model 11 should be thoroughly discussed with the Commanding, Engineering and Ops personnel and may require system level changes beyond what is capaable in the proposal.

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