URSI Boulder Jan 2006 The Iowa e-SRT laboratory Robert Mutel, Laura Spitler*, Kevin Ivarsen †...

URSI Boulder Jan 2006

The Iowa e-SRT laboratoryRobert Mutel, Laura Spitler*, Kevin Ivarsen†

University of Iowa

* Now at MPI, Bonn† Now at UNC


Summary• Astronomical lab course

– Mostly junior/senior undergrads– 1/3 each: data analysis, optical labs, radio labs– Optical half uses Iowa Robotic Observatory– Radio half used modified Haystack SRT (‘e-

SRT’)– Also teach ‘science-based’ radio astronomy

course

• e-SRT– Hardware modifications

• Optical encoders added• Digital receiver replaced with ‘traditional’

super-heterodyne receiver• Spectrometer replaced with 1024 channel

autocorrelation receiver (USB interface)

– Software modifications• JAVA-based Haystack system replaced with

Python modules • Spectrometer control uses C

– Curriculum examples


Iowa Robotic Observatory(located 50 mi SE Tucson AZ)


Radio astronomy labs:LC filter

Filter ‘Lite’ Program


e-SRT Telescope modifications

• Elevation axis

• inclinometer (±0.1° resolution)

• Serial interface

• ~ $100

• Azimuth axis

•10-bit absolute encoder (US Digital)

• ~ $200


e-SRT receiver system I: Front-

end Box


e-SRT Receiver II: IF Rack


e-SRT IF Rack


e-SRT III: 1024 channel auto-correlator

• Uses ‘quaint’ CMOS correlator (UNM 1993, also used at GBT)

• 1024 lags, 2 or 3-level, 100 Ms/s max.– e-srt mode:

• 4Ms/s (2 MHz = 422 km/s range)

• N x 0.523 sec integrations

• Output I/O either PCI or USB• Correlator software written in

C• Still in development

– Overheats unless reset pulse applied on power-up

– Occasional random failures– USB interface not complete


e-SRT Telescope control software

• Written in Python 2.3 (with WX-Python for GUI)

• Runs on Linux/Windows/Mac

• More flexible control of telescope

• (Probably) easier to modify on-site

• Correlator control software currently in C (port to Python in progress). May not be portable.


e-SRT software: Scripting and web-scheduled operations


Lab project write-ups (available on web)


e-SRT observational projects I: Spillover temperature and telescope beamwidth using Sun

FWHM = 5.1°± 0.1°


e-SRT observational projects II: Mapping HI 21cm emission along galactic plane


HI 21 cm longitude-velocity plot along galactic plane


Mapping the local spiral arms


HI Column density sky plot


Finale: Field trip to North Liberty Iowa VLBA site!

e-SRT to scale


Summary• Goal: redesign SRT to more closely emulate

‘standard’ radio telescope• SRT modifications:

– Telescope: optical encoders for better positioning (no homing needed)

– Receiver: replace with super-heterodyne, • Add many test points, 50 ohm load, test signal injection

– Correlator: replaced with 1024-channel autocorrelator• Faster than SRT receiver (all 1024 channels available)

– Software: Replaced JAVA code with Wx-python • more modular, • also transportable, • added user features

URSI Boulder Jan 2006 The Iowa e-SRT laboratory Robert Mutel, Laura Spitler*, Kevin Ivarsen †...

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