Total power vs time from aerostat radar

        The aerostat is a tethered balloon radar that flies above lajas puerto and is used for drug interdiction (more info).

    On 06oct04 data was taken with the radar interface (RI) using pixel 2a,2b of the alfa receiver. The band was centered at 1410 Mhz. The control room front panel outputs were passed thru attenuators (pix2a 15db, pix2b 0b) and then the 300 Mhz band was detected with a 20 usecond time constant. The detected  signal was then sampled at 10 usecond sampling for 48 seconds. During the data taking,  the telescope was parked at az=270, za=1.9 degrees.

    The attenuated version was to let us see an unclipped version (in the A/D's) of the radar signal when it pointed at the AO.  The unattenuated version was to see detail when the radar was not pointed directly at us. These plots can be used as a reference when someone is looking at  a square law detected signal on the oscilloscope in the control room. This data set includes all the radars in the 300 Mhz band. The discussion below is limited to the aerostat radar.
    The plots show the 300 Mhz detected band versus time (.ps)  (.pdf) :

• Fig 1: The first figure shows the entire 48 seconds. The red lines are where the aerostat points at the observatory (and is blanking). The green lines are 108 degrees before the observatory direction while the blue lines are 115 degrees after the AO direction.
• Fig 2: This shows the 4 times the aerostat pointed at the observatory. The blanking lasts for about 1.4 seconds.  The relative size of the signal on both sides of the blanking region shows how well the blanker is aligned with our direction (it looks pretty good here).
• Fig 3,Fig4: These are the signals from the aerostat when it pointing -108/+115 from the observatory direction. Since it is symmetric about the AO position, it is probably from a sidelobe/backlobe of the transmitter rather than a reflection from a tower.
• Fig 5: The top figure shows 8 contiguous ipps. It shows the 7 ipp sequence of the radar. The measured values are within the time constant of the values measured with higher time resolution. The bottom plot shows a single pulse. It is 367 useconds wide. This is close to the expected width of 320 useconds (given the time constant).  The two peaks come from the two different frequencies (160 useconds one frequency followed by 160 of the second).