Making MOPRA go!

Lucyna Kedziora-ChudczerFriend of the telescope

(UNSW)

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: 280m

● Pointing accuracy 10''

● Max operational wind 8.4 m/s

Atmospheric opacity measured with 'skydips'

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,eff

=Tamb

(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

Frequency switching

40 sec interval

20 sec interval

Pointing corrections from observations of SIO masers

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

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

weather receiver software observer0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Time lost due to:

Observing parameters for the MOPRA antenna

Frequency 86 GHz 96 GHz 115 GHzFWHP Beamwidth 34'' 30'' 25''Tsys (at zenith) 143 K 177 K 299 KSensitivity (Jy/K) 43 62 111Zenith opacity 0.102 0.121 0.180Continuum 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)

Examples of moleculesfound in the Hot MolecularCores

Future developmentsUpgrade 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