Making MOPRA go

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Making MOPRA go!

• Lucyna Kedziora-Chudczer
• Friend of the telescope
• (UNSW)

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MOPRA at mm wavelengths

• 22-m diameter telescope
• Location 20 km from Coonabarabran (NSW)
• Altitude 850m
• SIS receiver (helium cooled to 4 K)
• Operates between 86-115 GHz
• Digital correlator (max bandwidth 256 MHz)
• Surface accuracy 280?m
• Pointing accuracy 10''
• Max operational wind 8.4 m/s

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Atmospheric opacity measured with 'skydips'
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Observing strategy at the MOPRA telescope

• Observing modes for spectral line observations
  position switching, frequency switching or
  mapping
• Calibration method of the system temperature is a
  variation of a 'chopper wheel' technique, which
  uses a blackbody source at ambient temperature (a
  paddle) to correct the antenna temperature for
  atmospheric attenuation
• 
  Tsys,effTamb(Psky/Pamb-Psky)
• Absolute flux density calibration is achieved by
  observations of planets or other sources of known
  flux density
• Pointing calibration is applied by observations
  of SIO masers every two hours
• More information in the Mopra User Manual (MUM)
• www.phys.unsw.edu.au/astro/mopra/mum/
  manual.html

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Frequency switching
40 sec interval
20 sec interval
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Pointing corrections from observations of SIO
masers
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MM winter season 2002

• 29 Jun - 10 Nov
• Started with the 4-day Workshop (24 -27 June)
• 102 days scheduled for the mm receiver
• 75 of this time used by the UNSW
• The UNSW observing program
• Survey of hot molecular cores (HMC)
• Search for biomolecules (propylene oxide)
• Kinematic distances to medium-mass star
• forming regions

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Efficiency of observing

• 80 of time the data was acquired
• Half of that time the observing efficiency was
  higher than 50
• However 30 of that time the observing efficiency
  was less that 20
• Possible reasons
• Weather (mostly gusty winds)
• Observing project and strategy constraints
• Large overheads due to 'labour intensive'
  operation of the telescope

Time lost due to
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Observing parameters for the MOPRA antenna
Frequency 86 GHz
96 GHz 115 GHz FWHP
Beamwidth 34''
30'' 25'' Tsys (at
zenith) 143 K
177 K 299 K Sensitivity
(Jy/K) 43
62 111 Zenith opacity
0.102 0.121
0.180 Continuum flux sensitivity
0.54 Jy 1.34 Jy
2.99 Jy (1 sec, 64 MHz, 2IF) Line flux
sensitivity 154 mJy
258 mJy 622 mJy (10 mins, 10 km/s, 2
IF) Line brightness sensitivity 5 mK
6 mK 8 mK (10
mins, 10 km/s, 2 IF)
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Examples of molecules found in the Hot
Molecular Cores
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Future developments

• Upgrade of the telescope control software
• Replacing ACC
• Reduce number of computer operating systems at
  Mopra
• Make observing and calibration more automated
• On-line data reduction software
• Upgrade of the receiver tuning software
• Resolution of the coma distortion problem
• Building a new filter bank
• Enabling the rapid frequency switching controlled
  by the receiver hardware, not by the rate of
  correlator data readout
• Enabling beam switching
• New synthesizer which can replace the L4 LO chain
  in order to observe two different frequencies at
  two channels simultaneously

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