Amateur Radio Astronomy: Astropeiler Stockert The Stockert Radio Observatory

Jürgen Starek Astropeiler Stockert e.V. 2013

Astropeiler Stockert

Astropeiler Stockert

Who's there? Astropeiler Stockert e.V. • Since 1995 • Only unpaid volunteers • ca. 150 members, ca. 25 active – Amateur radio enthusiasts – Scientists – Electricians – Teachers – ...

NRW-Stiftung • Owner of buildings and observatory grounds since 2005 • Main financial sponsor – financed through membership fees, donations, lotteries

• excellent cooperation

Astropeiler Stockert

Radio Astronomy: A bit of background

Astropeiler Stockert

A very short history • Phenomenon was suspected following Maxwell's equations • 1930: Accidental discovery by Karl G. Jansky • 1937: Grote Reber builds 9m dish, creates first radio sky map • After WW II: Use of old German “Würzburg Riese” radars Bild: WP-User Charly Whisky, http://de.wikipedia.org/wiki/Bild:Mvc-471x.jpg

Astropeiler Stockert

Historical context of the Instrument

1955: Berlin Adlershof 35 m meridian dish

1961: Parkes 64 m fully steerable 1956: Stockert 25 m fully steerable

1963: Arecibo 300 m fixed dish 1973: Effelsberg 100 m fully steerable

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Away from single parabolic dishes

1978: VLA 27x25m on rails

2010: ASKAP SKA prototype

2010: LOFAR Pure interferometer, simplest antennas, Computing: BlueGene/P at Groningen

2013: ALMA movable 12m dishes

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Parabolic antennas • Prime focus system – Receiver Feed in focus point • Offset-mirror – Feed in prime focus • Cassegrain systems – Auxilliary mirror behind prime focus – Feed in secondary focus

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Simple radiometers The conceptually simplest radiometer consists of three stages in series: – an ideal (lossless) bandpass filter that passes input noise only in the desired frequency range, – an ideal square-law detector whose output voltage is proportional to the square of its input voltage; that is, its output voltage is proportional to its input power, – and a signal averager or integrator that smoothes out the rapidly fluctuating detector output. (http://www.cv.nrao.edu/course/astr534/Radiometers.html)

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Simple Radiometers

(http://www.cv.nrao.edu/course/astr534/Radiometers.html)

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Dicke Radiometer

(http://www.cv.nrao.edu/course/astr534/Radiometers.html)

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Measurements

Intensity

• Time • Position • Power – here: “continuous”, as measured by radiometer

Time

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Taking spectra • In 1958: Switched filterbanks – Hours • Today: FPGA-based FFT spectrometer – Seconds

Bild: “Technische und astronomische Messungen mit dem Bonner 25-m-Radioteleskop”. Mezger, Mitteilungen der Universitäts-Sternwarte Bonn Nr. 25, 1958.

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Cosmic radio emissions • Unmodulated signals – Thermal Radiation – Synchrotron Radiation • plasma around magnetic stars – Supernova remnants – Pulsars

– Absorption and emission in gas clouds • esp. neutral Hydrogen (HI): 1420 MHz • OH-Maser at 1.6-1.7 GHz

The Stockert Observatory

The site and its history

Astropeiler Stockert

Relevance in post-war Germany • First dedicated radio telescope in Western Germany • Demonstration of economic power • End of Allied ban of radar research • First secret radar experiments of the young Bundeswehr

Astropeiler Stockert

Use of the observatory • Fundamental research – University of Bonn – Max-Planck-Institute for Radio Astronomy • 2nd rate programmes and tests after comissioning of Effelsberg (1972) • Uni Bonn retreats in the 80s => Years of neglect – Remodeling? – Demolition? • 1995: Status as historic monument • Company headquarters – some renovation – but lots of dismantling

Astropeiler Stockert

Renovation and Recomissioning • 2006: Start of work • 2007: Major steel structure rework • from 2008: Complete redesign of control system and measuring equipment • from 2009: Major renovation work on secondary buildings

Astropeiler Stockert

Astropeiler Stockert

Astropeiler Stockert

Astropeiler Stockert

Inside the telescope

Telescope control, receivers and other systems

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Drive system • “Amplidyne” generator set • AC motors • Classical gear drives

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Control System • • • •

New electrics, old mechanics Current industrial standard self-built Siemens S5 PLC

Astropeiler Stockert

Manual control desk • Simple systems • Completely self-built

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Computer controlled drive system • • • •

Scans, pointing model Self-developed control program Python Text interface

Control program

Siemens S5 PLC

M Amplifier

Amplidyne M

A-/D-card Incremental Sensors

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New receiver • FGAN 1,3-1,4 GHz, not cooled, low maintenance • Standardized box • Overhaul in early 2012

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AFFTS • FPGA spectrometer • Direct-to-GigE

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The 1420 MHz hydrogen line

Astropeiler Stockert

Emission of neutral hydrogen clouds • Spin flip in neutral H – forbidden transition – de-excitation emits photon at 21 cm wavelength or 1420 MHz – excited state lasts ca. 11 Ga – despite low column density, length of gas column provides continuous radiation • Advantage: permeates dust, look into “cold universe”

Astropeiler Stockert

Cold hydrogen in our galaxy

Measured 14. Sept 2011 , Stockert

Astropeiler Stockert

At a different place...

Measured 14. Sept 2011 , Stockert

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Cloud rotation

Bild: O. von der Lühe; Universität Heidelberg

Astropeiler Stockert

Hydrogen emissions from different galactic lengths

Grafik der Milchstrasse: NASA / JPL-Caltech

Measurements 29.9.2011 , Stockert

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Astropeiler Stockert

Pulsars

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Basics • „In spite of almost four decades of intensive research on pulars, it is a fair statment that pulsars are only understood poorly“ (Michael Kramer, Duncan Lorimer, Handbook of Pulsar Astronomy, 2005)

• Basically: Rotation of magnetic field through free charge carriers around the star causes synchrotron radiation

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The problem of dispersion • Wide-band measurements desirable for greatest energy sum • Interstellar medium selectively influences different frequencies

(De-Dispersion)

F4 F3 F2 F1

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Simplified workflow

Figure from: “Binary and Millisecond Pulsars at the New Millennium”, Duncan Lorimer, 2001. arXiv:astro-ph/0104388v1

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An example showing double pulses

PSR B2020+28

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Most recent (March 2013): Giant pulses

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(Computing) lessons learned • There is neither compellingly good hardware nor compellingly good software for machine control. • Version control and Software Engineering concepts are not well accepted in the community. • Scientific software is unneccessarily “forced to age” by systems development. • FPGAs are extremely potent platforms for parallel computation and signal processing.

Astropeiler Stockert

Questions? • Contact us: http://astropeiler.de [email protected]

• Many thanks to all supporters! This project would not have been possible without the help of a lot of people in and close to our club, the NRW-Stiftung, the Deutsche Stiftung Denkmalschutz. Experts from the Universities of Bonn, Aachen and FH St. Augustin as well as Effelsberg and Jodrell Bank observatories and the Fraunhofer FHR in Wachtberg provided invaluable feedback, information and technical know-how. A lot of anonymous guests and supporters have donated to our project, providing essential funding for our work. We are also grateful for all the patient support provided by our project management. Last but not least, we thank all the people involved in planning, building and operating the telescopes for their solid engineering.