lancaster university department of communication systems skymap at 38.2 mhz as measured by iris...

Lancaster University

Department of Communication Systems

Skymap at 38.2 MHz as Measured by IRIS

Steve Marple



Skymap

A skymap is a map of cosmic noise level in all directions.

• Required to generate theoretical quiet day curves* (QDCs) for riometry and system design

• Uses in astronomy, e.g., observing large-scale galactic features

* QDC: background cosmic noise level in absence of absorption.



Skymap [Cane, 1978]

0.2 0.4 0.6 0.8 1

30

210

60

240

90 270

120

300

150

330

180

0

15

20

25

30

35

40

45

50

55

Temperature (1000’s K)



Jodrell Bank Radio Telescope

Kilpisjärvi

Jodrell Bank

Lindau



IRIS (Imaging Riometer for Ionospheric Studies)

• 64 crossed dipoles• 49 imaging beams• beam width 13° ~ 16°• 6+ years of data• Declination range:

14.1° - 83.3°N



Beam projection

12oE

16oE 20oE 24oE 28oE

66oN

67oN

68oN

69oN

70oN

71oN

72oN



Received power affected by:

• Solar controlled D-region absorption

• Snow (modifies antenna performance)

Mean QDC Power and Snow Depth00:00:00 UT 02/09/1994 - 00:00:00 UT 01/01/2001

Kilpisjärvi, Finland (69.05° N, 20.79° E)

-110.5

-110

-109.5

-109

Po

we

r (d

Bm

)

1/1/1995 1/1/1996 1/1/1997 1/1/1998 1/1/1999 1/1/2000 1/1/20010

0.5

1

1.5

2

date

Sn

ow

de

pth

(m

)



IRIS Skymap



Cane and IRIS skymaps

0.2 0.4 0.6 0.8 1

30

210

60

240

90 270

120

300

150

330

180

0

15

20

25

30

35

40

45

50

55

Temperature (1000’s K)



Summary

• Sky maps are needed for theoretical quiet day curves and system design

• An imaging riometer has been used as a radio telescope to produce a skymap

• Using riometer data from Antarctica a matching southern hemisphere map could be made

lancaster university department of communication systems skymap at 38.2 mhz as measured by iris...

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