This occasional series focuses on members of the Frontier Fields team.  It highlights the individuals, their jobs, and the paths they took to get to where they are today.   

What is your position?

My formal title is Research & Instrument Scientist in Hubble Space Telescope’s Instruments Division. I help manage the Frontier Fields data pipeline, which delivers the best possible calibrated data products to the astronomical community. I am also part of the WFC3 [Wide Field Camera 3] Instrument team where I work on calibration of the UVIS [ultraviolet and visible light] and IR [infrared light] detectors.

What is a “data pipeline” and what does it mean to “calibrate”?

A data pipeline is a set of software for processing and combining sets of images. It includes tools to correct for instrument artifacts, such as bad pixels, thermal signal from the detectors, and variations in sensitivity across the field of view. The goal of calibration is to tie the brightness of objects measured in Hubble’s cameras to some absolute system, based on measurements of stars of known brightness.

What does a typical day on the job entail? What are your responsibilities?

The data pipeline team keeps an eye on the Frontier Fields images as they are arriving from the telescope. For a given cluster, these come in a steady stream over a period of about 6 weeks, so we have to keep on top of things. First and foremost we need to be sure that the telescope was pointing in the right place and that it was stable throughout the exposure.

We also develop software to correct the images for artifacts that aren’t automatically handled by Hubble’s standard calibration pipeline. This includes masking out artifacts like satellite trails or scattered light from bright stars. We also mask IR ‘persistence’ which is leftover signal from very bright objects in observations taken just prior to ours. For the IR detector, we correct the images for stray light, usually from the bright Earth, that varies with time over the course of an exposure. For the ACS [Advanced Camera for Surveys] detector, we correct for artifacts like hot pixels and charge transfer losses during readout, both of which are considerable after being in space for 13 years.

Once that is complete, we correct the images for distortion and align them. These are then stacked together to create full-depth mosaics for each filter using specialized software called AstroDrizzle which allows us to optimize the resolution of the final images.

What specifically is your background?

I have a BS in physics and an MS in astrophysics. I’ve been at Space Telescope since 1996, and over the years have helped calibrate Hubble’s main imaging cameras: WFPC2 [Wide-Field Planetary Camera 2], ACS, and now WFC3.

What particularly interested you in school or growing up?  What were your favorite subjects?

I was particularly interested in science and math in high school. I remember in physics class we had to predict the landing spot of a marble rolled down an inclined plane and off of the side of a table. Measuring only the height of the incline, the height of the table, and the time the marble was in the air, we were able to calculate where on the floor the marble would land and then put a paper cup there to catch it. I was amazed that this actually worked and was struck by the power of mathematics to predict events which seemed like magic to me.

How did you first become interested in space?

My birthday coincides with the peak of the Perseid meteor shower. This is a particularly spectacular event in southwest Colorado where I grew up, and when I was little I asked my mom if the meteors were special for my birthday. She cleverly told me that they must be, and that felt very magical to me. When I got older, friends and I would hike to the top of a mountain and lay back to get a full view of the night sky. As the meteors streaked across the sky, we would imagine that we were clinging to the side of the Earth, spinning at 1000 miles/hour, and trying not float away into space. Growing up under really dark skies really sparked my curiosity about space and made me think about all the mysteries still undiscovered.

Was there someone (parent, teacher, spouse, sibling, etc.) or something (book, TV show, lecture etc.) that influenced you in developing a love for what you do, or the program you’re a part of?

When I was young, I asked a lot of questions and especially wanted to understand how and why things worked. My parents never said “I don’t know,” but took the time to show me how to find answers, either in books or on the computer. We watched a lot of nature documentaries together, including the original Cosmos series which resulted in a lot of interesting discussions. My parents really listened to my questions and as a result instilled in me a general curiosity and love of learning.

Is there a particular image or result that especially fascinates you?

I’ve always been fascinated by galaxy clusters, and the Frontier Fields images are pushing the limits of HST’s instruments to the extreme. By combining very deep exposures with the power of a gravitational lens, we are able to look back even further in time to view galaxies when the Universe was only 500 million years old. When you create very deep images like these, limitations in the current instrument calibration become apparent. We are developing new techniques to do cutting-edge calibration and sharing these new methods with the user community in the hope of allowing for the best possible science with HST. It’s exciting to be a part of all this new discovery!

Are there specific parts of the program that you’re particularly proud to have contributed to?

In addition to my Frontier Fields work, I’m proud to be a member of the Hubble Heritage Team, which produces some of the most iconic astronomy images ever. These images are designed specifically for the purpose of inspiring people, and I think that is an especially worthy pursuit! My specialty is in understanding Hubble’s instruments, and I work on designing the observations and also in calibrating and aligning the images once they have been acquired. Some recent mosaics I’ve had the pleasure of working on include hits like the Eagle Nebula, Westerlund 2, the Monkey Head Nebula, and the Horsehead Nebula.

Is there anything else that you think is important for readers to know about you?

I have a 5-year-old son who loves space and especially playing Lego “Hubble Rescue” to reenact the servicing missions. One of his more memorable quotes: “Hey mom, how about this time I be Mike Massimino and you be John Grunsfeld!” Being able to share my passion for astronomy with my son has been especially rewarding. [Editor’s note: Mike Massimino performed spacewalks on two Hubble servicing missions, and John Grunsfeld is a spacewalking veteran of three Hubble servicing missions.]

 For more information on the processing of Hubble images, please see these posts:

• Hubble Observations: From the Sky to the Ground
• Hubble Observations: From the Ground to Your Computer

For more information on how Hubble images are proposed, planned, and scheduled, please see these posts:

• How Hubble Observations Are Proposed
• How Hubble Observations Are Planned
• How Hubble Observations Are Scheduled