PDA

View Full Version : testing the WMAP beam profile



trinitree88
2009-Dec-05, 05:03 PM
Calibrating instruments is a necessary condition of observing, proving to oneself that what you think you are seeing is, in fact, there. It's not always straightforward with instrumentation in space because you rarely have a mechanic handy, and creating spacelike conditions in the lab are a little tricky. So people come up with different ways of calibrating instruments. This can lead to different theoretical interpretations of the subsequent data, which in turn leads to better calibration techniques. As usual, the two dance merrily forward towards the Holidays. see:http://arxiv.org/PS_cache/arxiv/pdf/0912/0912.0524v1.pdf

ngc3314
2009-Dec-06, 02:55 AM
And this aspect of astronomy remains the same. Quoting a letter from David Gill to J.C. Kapteyn, 18 January 1885:


But however perfect an instrument may be (and it is the astronomer's business to see that it is perfect), it is the astronomer's further business to look upon it with complete and utter mistrust.

trinitree88
2009-Dec-06, 05:04 PM
And this aspect of astronomy remains the same. Quoting a letter from David Gill to J.C. Kapteyn, 18 January 1885:

ngc3314. Yep. pete

Jerry
2009-Dec-06, 05:34 PM
The reasons for the difference between the radio source and the Jupiter beam profiles are still unclear. If the radio source profiles were then used to define theWMAP beam, there could be a dramatic change in the amplitude and position of even the first acoustic peak. It is therefore important to identify the reasons for the differences between these two beam profile estimates...
...The reasons for the difference between the radio source and the Jupiter beam profiles are still unclear. If the radio source profiles were then used to define theWMAP beam, there could be a dramatic change in the amplitude and position of even the first acoustic peak. It is therefore important to identify the reasons for the differences between these two beam profile estimates.

WMAP scientists planned to use Jupiter as a major calibration standard. But in the final 5-year analysis, there were virtual pixal-by-pixel thermal corrections, which are not generally to be considered to be a reliable post hoc tweek.

PLANCK has more fidelity built in to the on-board calibration system. Hopefully, when the data is wrung out, we won't see another round of 'we didn't get the data we expected, but we found new ways to standardize and here is the data we were expecting all along.'


it is the astronomer's further business to look upon it with complete and utter mistrust.
Obviously, not a student of the Carl Sagan school of belief in prior scientific achievements.