GBT Prime Focus RFI surveys

GBT Prime Focus RFI surveys - 2003

**Summary of RFI surveys**
Date	Band	Project Code	Backend(s)	Types of Data
2003 May 25	280-400 MHz	TGBT02C_002_01	ACS(200MHz)	Az rotation
2003 Jun 17	700-900 MHz	TMIT_RFI_800	ACS(200MHz)	Az rotation
2003 Jun 23	700-900 MHz	TMIT_RFI_800_02	ACS(200MHz)	Az rotation
2003 Jul 03 (night)	280-400 MHz	TMIT_RFI_340	ACS(200MHz), PFS	Az rotation, el=6; Az fixed, el=77
2003 Jul 04 (day)	280-400 MHz	TMIT_RFI_340_02	ACS(200MHz)	Az rotation, el=6; Az fixed, el=77
2003 Jul 18 (night)	900-1240 MHz	TRFI_PF2_01	ACS(200MHz)	Az rotation, el=6; Az fixed, el=77
2003 Jul 18 (day)	900-1100 MHz	TRFI_PF2_02	ACS(200MHz)	Az rotation, el=6;
2003 Jul 19 (day)	900-1100 MHz	TRFI_PF2_03	ACS(200MHz)	Peaks, Off/On
2003 Oct 19 (night)	400-450 MHz	TRFI450_101903	ACS(50MHz)	Az rotation, el=7;
2003 Oct 19 (day)	400-450 MHz	TRFI450_OCT19	ACS(50MHz)	Az rotation, el=7;
2003 Dec 02 (day)	500-700 MHz	TRCO_2DEC03	ACS(200MHz)	Az rotation, el=7;
2004 Feb 24 (night)	700-900 MHz	TRCOFEB24	ACS(200MHz)	Az rotation, el=7;

All ACS spectra done with 200 MHz bandwidth, 1-second noise switching, 2 second integrations, 1080 arcmin/min az rate (i.e, one 360 deg rotation in 20 minutes).

Download ascii files

Each of these files, when "gunzip"ed and un-tarred, becomes a directory with 600 ascii files, each file contains 4 spectra taken at a particular azimuth. The file has a header indicating the azimuth and time. The data have been calibrated and are in units of Janskys, i.e., 10**-26 watts per sq. meter per Hz. The columns in the table are 1) frequency, next spectral data in 2) Left circular polarization, 3) right circular polarization, and columns 4) and 5) is the same data with an 11-point median subtracted.
Data from May 25. Sweep in azimuth at 1080 arcmin/min. 600 spectra spaced (360/600) degrees apart. Elevation 7 degrees.
Scan 157, sweep from 90 to 450 azimuth. (49 MB)
Scan 158, sweep from 360 to 0 azimuth. (42 MB)

Some preliminary data from July 3.

Plot of raw spectrum averaged over 0 thru 180 degrees in azimuth, (elev=6 deg)
Plot of raw spectrum averaged over 180 to 360 degrees in azimuth, (elev=6 deg)
Plot of a single 2-sec integration at about 359 deg in azimuth.
PFS spectrum of 1 second of data corresponding to previous plot, at about 359 deg azimuth.

Note that the RFI spikes spaced at 2 MHz have been traced to the active surface controllers. These features are eliminated in subsequent runs by turning off the power to the active surface electronics. This is not a problem because the active surface is not needed at frequencies below 8 GHz.

Download sample PFS data

A binary file containing the first second of PFS data collected July 3 may be downloaded through this link (20 MB)

Summary Raw Data Plots

Azimuth spins averaged over all directions

Date	Band	Scans in average	Elevation
June 17 (Night)	750-850MHz	166,167	7.1°
June 23 (Day)	750-850MHz	39, 40	7.1°
July 03 (Night)	280-400MHz	19,20,21,22	6.1°
July 04 (Day)	280-400MHz	11, 12	6.1°
July 18 (Night)	900-1100MHz	31,32,33,34	6.1°
July 18 (Day)	900-1100MHz	27,28,29,30	6.1°