Transmitting to ISEE-3

“I VOLUNTEER AS TRIBUTE” is what Dana must have heard.

I probably said something to the extent of, “it sounds like fun to spend 2.5 hours sweating profusely in a barely ventilated dome in a confined space with a 400 kW transmitter requiring manual switching to talk to a spacecraft launched before my parents even considered having kids” or, “that might be fun to do later this week”. Not, “sure, I’ll go spend my afternoon plugging and unplugging a cord in the name of science and archaic flight hardware”. To Dana, this meant “absolutely, yes: today”.

Lunchtime conversations at Arecibo Observatory range from the mundane (“these pork chops are awful this week, save them for your dog; I’m getting a sandwich”) to scientific (“another way to think of the “dunite dilemma” is to consider that there may be an excess of olivine on Earth and that the asteroid belt is not actually depleted in this mineral”) to political (“… and that’s how we saved planetary radar at the observatory!”) to practical (“can we schedule that meeting for a time when everyone is around?”).

Dana’s usual henchman was away at a workshop in Berkeley building radio spectrometers with our favorite SETI hardware guy, so his usual partner in transmitter switching crime was gone.

I finished the press release draft about asteroid 2014 HQ124 we’d observed the day prior, a regular old asteroid but a real humdinger of a radar opportunity: predicted signal to noise of this object was in the tens of thousands per transit/receive cycle. My phone rang.

“Phil says we can go up now,” said Dana’s pitched voice. I ran over to the control room, grabbed a hard hat, and shoved a paper towel into the rim to catch sweat. We teetered down the hill to the cable car, waiting for our ride to the platform.

Late afternoon and the sky was mostly clear. Blue patches were hazy with Sahara dust, blown thousands of miles across the Atlantic and keeping it from raining here. When it rains you can’t go up to the platform, it isn’t safe, especially with the risk of lightning.  The afternoon looked clear, so we milled around the cable car building, waiting for our ride to the telescope platform.

Unlike in Goldeneye, the cable car doesn’t take off very fast: it’s a slow, steady ride up to the platform.  James Bond could have run up and down the catwalk several times before 006 reached the telescope platform via cable car.  A system of interlocks prevents the cable car from taking off without you.  After pushing the “up” button, the motor engages, wheels begin to spin, and the car gently lurches (if that’s at all possible) up a highly-greased cable.  Away from the cable car motor housing, you can just hear the squish of the wheels on the greasy cable and the jungle sounds below.

The dome grows larger and larger as the cable car ride continues, and eventually you hear the pulse tubes cooling the receivers in the dome.  My first night riding up the cable car in the dark I saw fireflies lazily drifting in the darkness below the dish.

She had some horses (Part I)

October 4, 2013


I traveled to Denver for the 45th Division for Planetary Sciences conference in October, conveniently located three hours east of a dear friend of my mother. I drove west from the airport as the sun set and the haze around Denver gathered, darkening from a dusty rose to grey to black.  I went over two mountain passes over 10,000 feet tall, feeling no ill effects as I adjusted to the altitude.  Around the tunnels of Glenwood Canyon it began to rain, far better than snow for driving, but still exciting as the Jeep hydroplaned and lost traction on the highway.  I continued onward and wound up in the tiny town of Silt, 97 miles from the Utah border with Colorado.

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How planetary radar works at Arecibo Observatory

We know Arecibo Observatory for its 305-meter (1000-foot) diameter telescope and its appearances in Goldeneye and Contact.  Aside from battling Bond villains and driving red diesel Jeeps around the telescope (grousing at the site director about the funding status of projects is optional), several hundred hours a year of telescope time at Arecibo go toward radar studies of asteroids.  Tasked to “find asteroids before they find us”, a group of us four planetary radar astronomers at Arecibo (as well as collaborators and colleagues at institutions outside of Puerto Rico) observes asteroids for NASA’s Near-Earth Object Observation program. We study the orbits and surface properties of our rowdy neighbors, near-Earth asteroids.

William E. Gordon telescopeHow do we transmit and receive radio waves using the klystrons and radio receivers at the observatory, and how do we turn these into images of asteroids?  Read more on my guest post at the Planetary Society on how planetary radar at Arecibo Observatory works.

ADS: How to find author names and affiliations

The astronomy and planetary science communities have a fantastic tool for finding scientific papers previously published: the Astrophysics Data System, or ADS, supported by NASA and run out of the Harvard-Smithsonian Center for Astrophysics.  The main feature I use is the abstract service, delivering summaries of papers and more.

The National Science Foundation requires that you include on some proposals the names of all of your coauthors from the last several years, as well as their institutions.  If you have more than a handful of coauthors, or are on publications with legions of coauthors, this task becomes difficult, and quickly!  Fortunately, as Leo Stein pointed out, ADS makes this process easy and even pleasant.

First, start an abstract search in ADS.  I’ll look up my fairy god-astronomer‘s coauthors, because they’re bound to be good folks.

ADS Search Page


Under Filters we’ll select only refereed articles, because we don’t want every last DPS and LPSC abstract.  For an actual NSF proposal, you want all bibliographic sources, as you don’t want a collaborator from a published conference paper being on the panel that judges your work.



We have a list of 68 abstracts!  Let’s go to the bottom of the page.



After the final abstract, we can select all records, or choose individual records for which to look up coauthor information.



Further down on the retrieved articles page, there’s an option to “Get Author-Affiliation form for selected articles”.




On the Author-Affiliation service page, you can select specific coauthors, and choose their current institution or affiliation, then finally export the whole kit and caboodle to a comma-separated text file (CSV), an Excel file (.xls), text, or to your browser.



Submit your NSF proposal, smile, then spend the time you saved to do some actual science.

I was first introduced to ADS in 2006 by Chi “Teddy” C. Cheung, and it’s been an indispensable companion since as I try to dig my way through a mountain of astronomical literature.  Export all of the references you want to BibTeX or Endnote format?  Keep a library of papers?  Find out if your friends have been publishing lately?  Massage your toes?  ADS does all of that, and more.  I am tremendously grateful for the grants that enable ADS to continue running and providing these services to our communities.

What is your favorite ADS trick or feature?  Feel free to share in the comments.

Scoping out the rowdy neighbors and baking Apophis cake

It’s been a pretty exciting week to be an asteroid researcher: you’d think the sky was falling!  Really, it was just a confluence of some rowdy neighbors checking in on earth asking, “How’s that space program coming?”  An ordinary chondrite meteorite exploded over Russia, and later that day a 150-foot-wide piece of spacerock skimmed 17,000 miles above the earth, just ducking inside the orbits of geostationary satellites.
We had nothing to do with either: the Russia bolide was detected maybe seconds beforehand by some satellites; 2012 DA14 was too low in our sky for Arecibo to observe.

The media guy here is still getting calls, almost a week later.  Univision came by, Dish Network wanted to interview someone…
Inline image 1 What are we doing in the midst of all this?  Regularly scheduled observations of asteroid (99942) Apophis, everyone’s favorite potentially hazardous asteroid that we’ve known about for almost nine years now.  None of these recently discovered raucous interlopers for us this week, pshaw.  Even so, the events of last week underscore the importance of “finding them before they find us” and commercial solutions to asteroid problems.
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Sailing on the seas of Titan

It’s past 3 am and we’re observing asteroids with the Arecibo planetary radar system. In the lulls between experiments, Twitter conversations covered everything from the Russian bolide explosion, 2012 DA14, Toutatis, rain on Titan, and some jokes about sailing on Saturn’s largest moon. The sky is falling, what else will you talk about?

Who would run the Titan sailing expedition?  I suggested myself and nominated Sarah as admiral; an aeronomer offered to be railmeat.  Cracks about how we’d all be “squidbate” went back and forth.  Brian christened our ship “The Calamari”.  Alex designed a mission badge.

Before I knew it, Justin “@UrbanAstroNYC” Starr had turned the whole conversation into a meme.

From @UrbanAstroNYC, “Sondy and friends go sailing on Titan”, with apologizes to Charles Schultz

My grandfather Bill Littlejohn used to animate Peanuts; he would have been 99 this year.  An animator, union organizer, test pilot, and airplane designer, his long and varied career reminds me that it’s okay that mine is taking a variety of twists and turns through technical and creative pursuits.  Bill grew up in a sailing family, and a few of his hand-illustrated birthday cards that he’d mail or fax every year involved sailboats and depictions of me with short brown hair.

Thank you, Grandpa, for all you created and gave; you’re living on as we continue to explore the cosmos.

Guiding out the waves: engineering planetary radar

I spent last week observing of asteroids from the telescope: our first night was just another 8-4 workday night, where we looked at space rocks in our neighborhood and out beyond Mars for eight hours.

Arriving at the control room, I sat down with my binder full of… notes on how to observe at Arecibo, which hadn’t made much sense.  At any optical observatory you enter your coördinates into a computer and take an image.  After verifying that you pointed the telescope correctly, you then tell the telescope system to take data for the rest of the night, occasionally adjusting pointing or focus.

Hector está llamado por telefono

At Arecibo, you’re pointed in the right direction.  Alignment with the William E. Gordon Telescope is not an issue.  Even with the 305-meter dish, you’re good to a few millimeters.

Position of the platform, receiver, transmitter

Getting the signal out of the receiver and properly into the computer is the hard part of observing.  Instead of a few shiny silvered mirrors and a charge coupled device digitizing and sending your photons to a screen, here a maze of waveguides, cables, and wires brings signals from the matte metal dish, after being ushered into the receivers, along a path 1,600′ long to the control room.  Where computer monitors would display starfields at an optical observatory, wavy lines danced across oscilloscopes at Arecibo.  It felt like junior year electronics laboratory again in the physics department, so different from most of the things we were doing in astronomy, and not just because of cgs/MKS units arguments.

Ellen had considered walking me through cabling the week before our six-night-long marathon observing run, but ultimately decided that it wouldn’t make sense out of context.  Wait for the actual observing run to understand the cabling.


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A week at Arecibo Observatory


A little over a week ago I arrived at the largest single-dish radio telescope in the world.  My boss picked me up at the airport and drove me up into the hills of Puerto Rico’s karst country where I caught my first glimpse of the support towers of Arecibo Observatory, peeking out over the wooded hills.

8 o'clock tower

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National Optical Astronomy Observatory of Japan

May 22, 2012


Just a few kilometers down the road from JAXA where I’d spent the summer of 2011 was 天文台通り, “heaven language hill avenue”.  By some combination of my lack of kanji comprehension and the supreme focus of my colleagues, no one put one and one together and so during my first seven weeks in Japan I managed to be unaware of the proximity of the National Astronomy Observatory of Japan.  I fortunately sat next to Ito-san at the ACM banquet, and he offered to give me a tour of the facilities.  I went back to see my old lab at JAXA, talked about the high quality of rice from Niigata, and was picked up by Ito-san in the midst of a rainstorm to visit NAOJ’s campus.

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