ECHO beam mapping is very repeatable. When we map two different antennas and subtract, the different is nearly zero. ECHO in blue, satellite measurements in grey.

Our first paper about the drone calibrator is out on the arxiv today!  Using data from our field tests last year we measured the stability and accuracy of the beam maps. The repeatability compared well to measurements made using satellites (thats the plot on the right) and the measurements matched up well with the models. There were a few issues though. The main thing seems to be the stability of the antenna attachment to the drone. We're sensitive to even a degree of rotation!  Overall, though the thing worked a lot better than I was expecting, quite frankly.

The paper is here: https://arxiv.org/abs/1610.02607

Last week the ECHO team took the (relatively) short drive from Tempe up to Prescott, Arizona and Embry Riddle Aeronautical University to do some more testing at a new location.  The Embry-Riddle Physics department has put together a very nice campus observatory which is predominantly devoted to radio science, both astronomy and aerospace. Under the leadership of Professor Andri Gretarsson, they have set up a set of three MWA tiles with which they plan to observe pulsars, and antenna elements from LWA and from LOFAR. On this trip we got shown around the site, made a preliminary map of one MWA tile, and discussed plans in the works to build a HERA dish.

Part of the ECHO team poses with an LWA antenna and the ECHO drone on the May, 31 trip to Embry Prescott, AZ. Left to right: Lauren Turner, Jacob Burba, Prof. Andri Gretarsson (ERAU), and Dr. Daniel Jacobs (ASU; ECHO PI)

We only had a few hours in the afternoon to map the tile, so we hurried through three sorties and hoped for the best.  Getting home and processing the data we were pleased to see the expected square sidelobe pattern (shown below). The errors are still a bit high due to a low sample count, so we'll be heading back up as soon as we can to get more data.

The beam map from this run. It came out surprisingly well for such a quick attempt at data collection.

ASU Students make adjustment to ECHO. Left to right: Ben Stinnett, Jacob Burba, Lauren Turner

This week several students and I traveled to Green Bank, WV for some high precision testing of the ECHO drone.  The goal was to test our beam mapping accuracy on an antenna for which we had good models.  This was also a week reserved for focused work; its our opportunity to put in a solid amount of time in the field to work out the kinks in the mapping process.  After some rain delays on day 1 the weather was beautiful for flying. Over the course of four days we flew around 25 flights and made four complete beam maps. This is described in more detail in our field report memo:

Report on ECHO measurements of Orbcomm dipoles in Green Bank. D. Jacobs (2015)

We had a good time and learned a lot; students and  PI.  Physics student Jacob took some truly excellent photos, check out the complete album here.

ECHO Green Bank trip 2015 Left to Right: Ben Stinnett, Danny Jacobs, Abraham Neben, Lauren Turner, Jacob Burba

About ECHO

ECHO is the External Calibrator for Hydrogen Observatories, a drone-mounted calibrator designed to help us get 1 part in 10,000 precision in cosmology telescopes targeting the first half-billion years of cosmic time. ECHO is supported by the National Science Foundation and Arizona NASA Space-Grant.

ECHO team members Mason Denny and Marc Leatham perform tests on a scale model testbed

This semester I start work in earnest on a new project thats been simmering in the background, the External Calibrator for Hydrogen Observatories (ECHO) an experimental method to provide an airborne calibration source for wide-field radio arrays observing Hydrogen at cosmological distances. In particular, accurate maps of the primary beam (the response of the receiver dipoles as a function of position on the sky) have been found to be crucial at multiple stages analysis of data from PAPER/MWA/LOFAR etc but have historically been measured through indirect means such as the amplitude of satellites or radio galaxies passing overhead. ECHO aims to provide a direct measurement with a system where all parameters are under the experimenter’s control.

At this point we are designing and building our transmitter (don't need much power for a radio telescope!) and selecting a new drone platform. We've hired a small team of undergraduates to take point.

ECHO team members Marc Leatham and Victoria Serrano give the quad-rotor a shakedown flight. The quad is acting as a scale model and training frame for a larger platform soon to come.

ECHO Version 1 A bicolog 5007 mounted on a 8 rotor Mikrokopter. An upgrade to a newer pixhawk-based platform is planned for the spring.

This project is supported by National Science Foundation and the Bowman Low frequency Cosmology lab in the School for Earth and Space Exploration.