This information can also be found in the ALMA User's Policies, Appendix B.

Please also see the 'May I make changes to my proposal?' KB article.

A change to an approved project that is initiated by the PI at Phase 2 is considered a major change if one or more of the following conditions are met for the requested change compared to what was submitted at Phase 1:

Target field location

• A shift in position of any pointing of more than 0.5 times the primary beam size.

Spectral windows

• A change to the central sky frequency of any spectral window that is more than 20% of the bandwidth of that spectral window.

• A change to a frequency setting or correlator mode.

• An increase in the bandwidth or spectral resolution of any spectral window (such changes should not impact the data rate).

Angular Resolution

• A change in angular resolution that is more than 10% of the requested angular resolution.

• Any change in angular resolution that would change the configuration from C-6 or smaller to long baseline (C-7 to C-10).

Observing time

• A change that results in an increase in observing time.

Other

• Any change that is not explicitly listed as a minor change below must be submitted as a major change request (e.g. changes to the default OT-generated observing parameters or observing strategies).

Any changes made are considered cumulative, e.g. a +2” change to the field center coordinate RA and a +1” change in the pointing offset RA will result in a +3” overall change in pointing position. 

Similarly, a -10 km/s change to the source radial velocity and a -5 km/s shift to a spectral window central frequency will result in an overall change of -15 km/s.

Changes that request capabilities that are not offered or that duplicate another observation ( ALMA User's Policies, Appendix A) are not allowed.

Minor changes do not change the project scientific scope, increase the observing time, or require a duplication check.

Minor changes initiated by the PI that can be made at Phase 2 by ARC staff without submission of a change request are as follows:

• Shifts in position of any pointing that are less than 0.5 times the primary beam size.

• Changes to the central sky frequency of any spectral window that are up to 20% of the bandwidth of that spectral window.

• Changes in angular resolution that are less than 10% of the requested angular resolution and that do not change the configuration to a long baseline configuration or increase the observing time.

• Changes to the source radial velocity, redshift or Doppler type that do not change the central sky frequency of any spectral window by more than 20% of the bandwidth of that spectral window.

• Trivial changes that do not imply a scientific impact, such as changing the velocity reference frame from LSR to Heliocentric