W E I S S E N A U S O L A R R A D I O A S T R O N O M Y O B S E R V A T O R Y *

(Report f rom Solar Institute)

H. URBARZ

Astronomical Institute of Tiibingen University, We&senau Observatory

(Received 1 November, 1968)

Weissenau Observatory is situated 1 km West of the railway station of Weissenau, a village on the Southern outskirts of the city of Ravensburg, 20 km North of Lake Constance. The surroundings of the Observatory are shown in Figure 1. It can be reached by car from Zurich airport by way of the City of Constance and the ferry to Meersburg within 3 hours.

There are two groups at Weissenau Observatory: the Atmospheric Physics Group and the Solar Radio Astronomy Group.

y o n von Ulrn T Libingen Biberoch

Weingarten

Ravensbur,

Bovendorf

Konsfonz Meersburg (aUs der Schwe~z) [from Swltzert(and)

Fig. 1.

Institut, VOn

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yon Fr iec}r]c hst~afen vcn L{ndau (QUS der Schweiz) TetLnan9 (from Switzer[Qnd) (QUS Osterreich)

(from Austrio)

Site of Weissenau Observatory (47o46 , N, 9035 , E).

* Mitteilung des Astronomischen Instituts der Universit~tt Tiibingen. Nr. 111.

Solar Physics 7 (1969) 147-152; �9 D. Reidel Publishing Company, Dordrecht-Holland

148 r~. URBARZ

1. Personnel

In the Solar g roup there are 4 scientific workers , G. Kr~imer, O. Meyer , H. Scheerer,

H. Urba rz , 1 engineer, J. Kr~imer, and 7 technicians and assistants.

2. Radiotelescopes

The ins t ruments used for solar obse rva t ion are a b r o a d b a n d rad io spec t rograph , a

number o f rad io te lescopes work ing on fixed frequencies, a two-e lement in ter ferometer

and a cosmic-noise abso rp t ion telescope. F igure 2 shows these ins ta l la t ions as seen

Fig. 2. The Radio Telescopes of Weissenau Observatory. The antennae of the fixed frequency total intensity telescopes are mounted on the three concrete pillars in the center foreground. The square fiat-roofed building behind the 3-m reflector houses the control and radiometer equipment. The azimuth-mounted antennae of the radio spectrograph are to be seen on a steel structure. The sweep radiometers and tracking equipment are housed in the cabin below the 7-m reflector. The two inter- ferometer arrays are to be seen near the right margin and near the riometer cabin at the 26-m horizon- tally set-up reflector on the left side, respectively. From the left background to the right there is a Laboratory, the main building of the Radio Astronomy Group, the Residence Hall, and the

Laboratory of the Atmospheric Physics Group.

f rom a po in t South o f the three an tennae o f the fixed f requency telescopes as well as

the steel s t ructure of the az imutha l ly m o u n t e d an tennae o f the r ad io spec t rograph

behind them. The sweep rad iomete rs are o f the non up-conver te r type bu t all solid

state. Table I is a summary o f the mos t impor t an t pa rame te r s o f the spec t rograph.

Al l types of burs ts o f higher than 100-200 flux units, m a y be identif ied clear ly on

film records. Magne t i c - t ape record ing o f digi t ized video da ta has been appl ied to

channel 2 giving a high dynamic range of flux densities.

The fixed f requency to ta l solar-f lux telescopes are to be seen in the fo reg round

of F igure 2. There are three concrete pedes ta ls with equa tor ia l ly m o u n t e d antennae.

The f la t - roofed bu i ld ing behind the centra l socket houses the rad iomete rs and an t enna

dr ive cont ro l desk, etc. Table I I shows the features of the fixed f requency telescopes.

Both quiet -sun level and burs t intensit ies are measured at 611 and 1000 MHz ,

whereas at m-waves only burs t intensit ies are measured .

WEISSENAU SOLAR RADIO ASTRONOMY OBSERVATORY

TABLE I

Parameters of the radio spectrograph

149

Channel n r ,

Frequency range (MHz)

Antenna system all vertical polarization RF to video amplitude train

32-46

46-86 86-160

160-290 290-540 540-950

broadband dipole and reflector

group of 4 fishbone yagis two full wavelength

dipoles and reflector 7-m parabolic reflector

with LP-feeder and triplexer

RF-filter octave bandwidth RF-preamplifier IF = 0 mixer and octave sweep oscillators (IF-bandwidth 10 KHz to 2.5 MHz max

so that BwRF/BwI~ ~ 200) Step attenuator Logarithmic IF-post-amplifier RC-integrator, video detector

video output and display

filming

time constant time resolution frequency resolution sensitivity dynamic range

High-speed sampling of 6 channels in sequence, which appear as 6 lines on the oscilloscope.

a fiber optic system transduces the 6 lines into one, which is filmed at 0.2 mm/sec speed with a 27/10 DIN film

1.5 msec on film - 0.25 sec on film - 100 elements, decreases with signal intensity on film - 100-200 • 10 2~ W/m 2 sec on film - 3 steps in the range of about 100-500 • 10 -zz W/m 2 sec

The two-element interferometer operates at 300 MHz with a 70-m basis, the two

dipole arrays are to be seen in Figure 2 on the extreme right margin and near the big

horizontal ly moun ted parabolic reflector feeding a 30-MHz riometer, respectively. The

meridian transi t of the sun is measured daily for about 3 hours by the fringes at 40'

interlobe. Though it is a power-adding instrument , the fringe response and the power

response of the transits are recorded separately on two recorders using a double

switched (1 KHz and 2.5 KHz) radiometric system.

3. Operation and CaLibration

There has been little effort in absolute cal ibrat ion of the records at fixed frequencies,

but some of the parameters of the telescopes are checked from time to time for

relative changes by system measurements. The burst records are compared with

absolute flux data of concomitant records of other observatories. The comparison of

all burst records above a level of 100-200 flux units with our own dynamic spectral

records is of great advantage, for erratic recordings caused by interference may be

excluded in this way.

4. Data Distribution

All impor tan t burst events are reported daily to the G e r m a n World Data Center of

the F T Z Darmstad t using U R S I G R A M codes U R A N A , U R A N E , U R A N T (modi-

fied). The spectral data are published by Solar Geophysical Data, ESSA, Boulder.

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W E I S S E N A U S O L A R R A D I O A S T R O N O M Y O B S E R V A T O R Y 151

All data, including those at fixed frequencies, are published monthly in the Bulletin of Weissenau Observatory.

Operation hours are from 5 to 19 UT in summer and from 9 to 15 in winter.

5. Research Programs

All measurements are made on a routine basis in principle, and a great amount of

dynamic spectra and burst profiles are obtained. For most of the scientific program the comparison of the dynamic spectral data with all available other solar data

associated with the events in question plays an important role.

Fig. 3. The big Polar Axis carries two sets of yagis and an array for meter-wave burst records.

Here are some outlines of the work carried on: The spectral behaviour and para- meters of type III bursts with harmonics are investigated as a function of helio-

graphic position and are compared with Wagner's theory of bipolar and quadru- polar emission of the fundamental and harmonic, respectively. From the frequency

152 H. URBARZ

drift of type II bursts magnetic-field values are derived using shock front theories. Special dynamic spectral features of type IV bursts are investigated for association with solar protons. Furthermore some statistics of type I burst chains between 200 and 250 MHz are gathered. A special program is devoted to digitized magnetic tape recording of dynamic spectra to achieve a high range of recorded intensities and to achieve automatic handling of the data.

6. Organization of the Observatory

Equipment and personnel were financed partly by the 'Deutsche Forschungsgemein- schaft, Bad Godesberg', partly by the Astronomical Institute of Tfibingen University, Federal State of Baden-Wtirttemberg, of which the Radio Astronomy Group is a constituent.