Ground Radiation and Interference and their change with directions

1. Ground Radiation and Interference and their change with directions Chen Wang JinLin Han, XiaoHui Sun, Wolfgang Reich, WeiBin Shi

2. Outlines • Reasons to do • How to do and what we did • Observation done • Ground radiation profile vs. Azimuth • Ground radiation profile vs. Elevation • Ground radiation at North Celestial Pole (NCP) • Interference from Indian synchronous satellites (INSAT) • Summaries

3. Why to study ground radiation? • Set up ground radiation model  absolute calibration. • Set lower elevation limit for observations. • Identify surrounding interference sources. • More?

4. How to do? • Scan along azimuth at fixed elevations. • Scan along elevation at fixed azimuths. • Monitor the NCP. • Mapping satellites.

5. Observations done • 36 scans along AZ • Generally, the separation of subscans is 2o (along EL ). • 12 scans along EL • typically EL = 5o– 81o , at a fixed Azimuth. • 24 scans at NCP • Some separate observations and a continual 34 hours observation. • 12 scans for Indian satellites • Four scans with size 10o *10o

6. Sky trajectory of observations NCP scans along EL scans along AZ Indian Satellites

7. I- AZ Ground radiation vs. Azimuth 12 EL=10 14 12 16 14 14 14 18 16 16 I 20 18 16 18 20 20 18 20 AZ

8. I- AZ Ground radiation vs. Azimuth Jump, Why? －Temperature? －Radome foil? 12 EL=10 14 12 16 14 14 14 18 16 16 I 20 18 16 18 20 20 18 20 AZ

9. Ground Radiation along azimuth at low elevation vs. the profile of the horizon of Nanshan Station I- AZ EL=14 I EL=16 EL=18 EL=20 The elevation of horizon at different azimuth

10. 350o 40o 320o 70o 290o 90o 253o 120o 240o 140o 210o 180o Ground radiation vs. Elevation • 12 scans distribute from 0o to 360 o • Observing avoid the Galactic emission (the same to scans along AZ)

11. SCAN 3578 AZ = 320o EL = 5o - 81o • Intensity changes exponentially with EL < 40o, and linearly with EL > 40o. • U & Q seems more complicated.

12. Ground radiation at NCP • The position of the NCP at sky keeps constant, so the ground radiation at NCP should be constant approximately too.

13. 34 hours Each of the four channels changes regularly daily －there are some strong sources near the NCP

14. UQ map of the NCP （not calibrated) • Except the ground radiation, the UQ map of sky emission should be a circle. (see the PhD thesis of Maik Wolleben)

15. The effect of satellites • Strong stripes in the south sky • Indian synchronous satellites at 4 positions, which all can emit in C-Band (just including our observing frequency). • Before the method to deal with stripes found, we have to observe avoid the south sky

16. INSAT_2DT Intensity INSAT_2DT Polarization Intensity

17. G193B G195B I1 channel I2 channel U channel Q channel I1 channel I2 channel U channel Q channel The stripes of satellites on the south sky at Nanshan Station

18. Summaries • Along AZ direction, the profile of GR corresponds with the profile of horizon. • Along EL direction, GR changes exponentially at EL < 40 and linearly at EL > 40. • The emission (including sky emission and ground radiation) at NCP changes daily. It’s hard to separate these two components. • Indian synchronous satellites disturb strongly to the observation at south sky • The research has just been done a little. More observation and study are needed.

19. THE END

20. The list of 12 scans along EL

21. The list of 17 scans at North Pole

22. The list of 12 scans of Indian Synchronous Satellites