NHSC HIFI DP workshop Caltech, 7-9 February page 1 Steve Lord Conversions of Intensity Scales and Frequency Units

- page 2 X-Axis Conversions HIFI can change the Spectrum Explorer labeling of a Spectral Data Set. –Can add an auxiliary axis (e.g. add LSB or IF or USB) –Can then alter that axis to show Velocity w.r.t. a reference frequency –See Developer's reference manual Chapter 8.1.1

- page 3 X-Axis Conversions We can use the command line to change the X- units of a data set: –ConvertFrequencyTask – HIFI Timeline Products or Spectral Data Sets –Converts between 4 views: USB, LSB, IF and Velocity –For velocity, user must specify Reference Frequency and whether that is in the USB or LSB (!) –see HIFI-um Chapter 8.2

- page 4 X-Axis Conversions We can use the command line to change the X-units of a data set: – ConvertWaveScale – Converts a Spectral Data Set –Converts between Frequency, Velocity (w/ref. f), Wavelength and Wavenumber [GHz, km/s, MHz, mm, m/s,1/m, MHz)] –See Developer's reference manual Chapter 2.77 –routine has some issues to be resolved for HCSS 6.0

- page 5 Changing Flux Units ConvertK2Jy has been implemented in 12/2010 Operates on Herschel Timeline Products and Spectral Data Sets Is entirely a HIFI routine Uses the fact that K "brightness temperature" converts to Jy/sr in the radio astronomy of using the Rayleigh Jeans approximation strictly, and the user can provide steradians. Uses the fact that the effective aperture is "known" for all HIFI frequencies, as well as beam efficiencies from using the HIFI cal tree. (This is accessed either locally or remotely – time consuming). Requires use input of a source size (diameter~HPBW ConvertK2Jy – has been implemented 2010

- page 6 ConvertK2Jy (con't) Basic Algorithm – 3 cases: The size in arc second of the source observed. 1) If the size = 0 the pointing like source formula is used: S/Ta (Jy/K) = 2k / (Ageom * eta_A), where: S is the Energy flux expressed in Jansky Ta is the Antenna Temperature measured in Kelvin k is the Boltzman constant, Ageom is the effective area of the telescope, which we have assumed to be 3.28m, so diameter. So, Ageom = 8.45m2 eta_A is the aperture efficiency, to be extracted from the calibration tree for the frequency of interest 2) If the size <= HPBW: S = Ta * 2k / (eta_B* size^2 /HPBW^2), where: eta_B is the Main beam efficiency HPBW is the Half Power Beam Width (HPBW) of the telescope expressed in square arc second 3) In case of size >= HPBW S ~= Ta * 2k / (eta_B* f_BEAM * lambda^2) f_Beam is the beam filling factor

NHSC HIFI DP workshop Caltech, 7-9 February page 7 Unit Conversion Tool for Herschel Runs alternatively: within HIPE – can take array as external JAVA tool as a website (server) Converts: Flux Flux Density Intensity Integrated Intensity Includes Help Files