When you make a time estimate HSpot connects with the server at the HSC to pass the information on the AOR and make the calculation of the time required to carry it out. You will need to calculate a duration for all your AORs before proposal submission and every time that the AORs are revised. For PACS and SPIRE the calculation is particularly rapid, especially in photometry mode. On a fast Internet connection time estimation for 500 PACS or SPIRE photometry AORs can be calculated in approximately 100 seconds. Time estimation for the same number of SPIRE PACS Parallel Mode, or PACS or SPIRE spectroscopy AORs will take from 150-200 seconds. Because of the large number of parameters in some HIFI AORs, the calculation is somewhat slower for HIFI: time estimation for 500 HPoint or HMmap AORs will take some 600-800s even if there is no other load on the system; while 500 HScan AORs will take in excess of 1000s. Even when several users are carrying out time estimation simultaneously and the system is under heavy load, the time required should not increase by more than a factor of two.

For PACS the time required to run a certain number of time estimates is generally slightly shorter than for similar SPIRE AORs: generally HSpot should carry out from 3 to 6 time estimates per second. HIFI runs somewhat slower due to the large number of parameters to be optimised, but will usually be in the range from 1 to 3 seconds per time estimate.