During this trip we moved another 32 antenna into the grid configuration. This array will be left running over the (southern) Summer until sometime in mid 2013. This should be enough data to make the most sensitive EoR measurement yet!

Also: I got to be co-pilot in an airplane!

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Today I needed a distraction so I transcoded some PAPER data into sound. It sounds really weird!

Cross-posted at asuexplorers.sese.edu

MWA_PAPER_sensitivity_croppedTitle: “A Per-baseline, Delay-spectrum Technique for Accessing the 21 cm Cosmic Reionization Signature”

This paper explains the PAPER method for measuring the EoR power spectrum. While some experiments plan on subtracting foregrounds, PAPER will stick to uncontaminated regions of power spectrum space. Narrow field simulations had previously expected this region to have little dependence on baseline length. This paper explains why in the wide-field case, foreground contamination gets worse with baseline length.

The PAPER strategy is to avoid this regime by concentrating sensitivity in a very dense array but sample longer spectral modes. In all this results in a comparitively lower SNR measurement (see right) but with better understood noise.

ADS linkpdf

Here is a helpful map of the radio sky I have been using to keep track of my MWA and PAPER observing. It has a few of the brightest sources, the seasonal position of the Sun, and what the sky looks like at midnight for each month of the year. Here it is hanging on my office wall.  The bigger the better!

I also made a map showing the footprints of the telescopes. They are so large, its easy to forget whats visible.
The images link to the full-size pdfs.

Title: A Sensitivity and Array-configuration Study for Measuring the Power Spectrum of 21 cm Emission from Reionization

sensitivity_I_summary_figurePAPER will soon be performing long integrations to the power spectrum of high redshift Hydrogen.  What is the best configuration?  In the process of answering this question we also carefully (re) derive the relationship between the output of an interferometer and the power spectrum. This settled (for us) some open questions about units and hopefully is another step towards building a stable bridge between theory and measurement.  However the takeaway is that, in the limit of a sensitivity starved interferometer trying to detect Fourier modes, a grid configuration can gain almost an order of magnitude in sensitivity.

Arxiv, pdf

As a follow up to the E1P launch, here is a small album of images from my time at the Montana State Small Sat Lab .


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At the Montana State Space Science and Engineering Lab I helped (as Project Manager) students from rural Montana to design, build, and fly a reflight of the first US satellite, Explorer I which discovered the van Allen radiation belts.  After 6 years of work and one failed rocket launch, E1P made it to space on 28 October 2011 and was rechristened the Hiscock Radiation Belt Explorer (HRBE) after Bill Hiscock, late director of Montana Space Grant and E1P patron.

Bill paid students to figure out how to build a satellite from scratch because he believed in them.   Several have gone on to work at NASA, SpaceX, and elsewhere.

News Articles

Here is a link to my PAPER thesis for posterity.  It included a catalog, as well as studies of calibration stability and noise properties. I included a lot of extra information about the 32 antenna catalog that was cut from the original letter.  Then, looking at 12 nights of data I found that despite high levels of cross-talk found in that early data PAPER is integrating down as expected.

The full pdf is available from Penn Scholarly Commons.

We’ve used data from April and September 2009 to make an image of the sky that covers 30000 square degrees. This is more than half of the entire sky! The results, including a list of the fluxes of known sources, are published in the Astrophysical Journal Letters.

The data are also available here:

We found that the fluxes agreed with previous measurements at about the 50% level which is about the accuracy you see when you compare between other catalogs at these wavelengths.

Onward to 32!

This month we added another shipment of 16 antenna to bring PAPER to 32 antennae.  The arrangement of the antennae on the ground is very close to random, making geography tricky!  I spent a good amount of time out there with the GPS pole and pack, marking out locations of antennae.  We also deployed 4 extra antenna to do a polarization experiment, but ran out of time. Literally and figuratively. First we barely got things running before we had to leave and then the timing turned out to be off by an unknown amount. Still, another great field season!


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