3.10 Bright-Object Constraints

Several of the Scientific Instruments must be protected against over-illumination. Table 3.13 summarizes the safety restrictions by instrument. You should not propose observations which violate these guidelines. Non-linearity, saturation, or other temporary effects which may occur at substantially fainter limits than those identified below are described in the Instrument Handbooks.

APT contains a Bright Object Tool (BOT) that can be used to check on these constraints. Proposers should check both the target and the entire field (35" radius from the target for a single default pointing at any orientation, larger plus 5" buffer with POS TARGs or other displacements), using the Aladin interface provided in APT.

Table 3.13: Bright-Object Constraints 

Instrument	Description
ACS	The ACS/SBC MAMA detector is subject to strict bright-object controls to prevent potentially fatal damage. Maximum permissible local and global count rates have been established for both imaging and spectroscopy; see the ACS Instrument Handbook (Section 7.5). These limits have been translated into a table of magnitudes as a function of spectral type for the various configurations and modes (ACS Instrument Handbook, Table 7.8). Some of these limits are quite faint. All potential targets should be checked for safety with the ACS Exposure Time Calculator on the Web. Measured UV fluxes must be provided for any objects within 1 magnitude of the spectroscopic limits. This requirement extends to both targets and field objects on the detector. ORIENTs and/or POS TARGs may be used to avoid the latter. Unless they can be screened with GSC2/DSS, magnitudes and colors, or a UV image, must be provided for all objects in the fields of proposed SBC observations, including the background fields of solar-system targets.
WFPC2	There are no safety-related brightness limits for the WFPC2. See the WFPC2 Instrument Handbook for a description of saturation levels, residual charge, etc.
FGS	The FGS may not be used to view objects brighter than mV = 1.8. The FGS may view objects brighter than mV = 8.0 only if the neutral-density filter is in place.
NICMOS	There are no safety-related brightness limits for the NICMOS. See the NICMOS Instrument Handbook for a description of saturation levels, residual charge, etc.