Imagining the future: gravitational wave astronomy

Shane Larson, PennState shane-at-gravity.psu.edu

On October 27-30, 2004, a group of 64 gravitational wave astronomers and astronomers from traditional fields of astronomy and astrophysics, representing 20 different institutions, convened at Penn State for a workshop to speculate on the future of gravitational wave astronomy. The purpose of the workshop was to begin a conversation in the community about the future evolution of the field of gravitational wave physics and astronomy, and to consider how this new observational science will fit into the toolbox of modern astronomers. The active pursuit of imagining the future, working outside of the confines of today's vexing research problems, helps to illuminate the road ahead so the needs of the field can be addressed in advance of the time when progress will be hindered or facilitated by the nature and quality of the infrastructure supporting the community as a whole. This type of endeavor is typically known as strategic planning.

The attendees were asked to consider a time two decades in the future, when gravitational wave astronomy is an established (but perhaps still adolescent) observational science that regularly contributes to our view of the Universe as an active component of multi-messenger astronomy. To facilitate discussion and debate oriented toward considering the future of the field, six questions were posed:

• What will it mean to be a ``gravitational wave astronomer''?
• What will be the interplay between gravitational wave astronomy and other, now conventional, forms of astronomy?
• What will be the interplay between instrumentation, observation, and science in the field?
• What will be the role of individual observatories vs. global networks?
• What will be the critical technologies used in gravitational wave detection?
• What infrastructure will best contribute to broad participation, community growth, and the best possible science?

After several days of open discussion and debate centered on these questions, several key findings emerged.

First, it is likely that in 20 years there may not be people who self-identify as ``gravitational wave astronomers.'' Instead, practitioners will become either instrumentalists or astronomers who tap gravitational wave astronomy as one element in a suite of tools used to probe the Universe. Today, the growth of multi-messenger astronomy is evident from cross-communication between electromagnetic bands and astroparticle astronomy. In an era where gravitational wave observations and detections are routine, it is not unreasonable to expect that gravitational astronomy will simply be another element which strengthens our ability to probe high energy astrophysical systems as part of multi-messenger observing campaigns.

Data products and data access were discussed at great length. Currently gravitational wave astronomy is operating with data products in which instrumental noise and astrophysical signal strength are comparable at best, and data analysis efforts require the expertise of people intimately familiar with the detectors. In the future, as instrumentation evolves and sensitivity increases, this model of data control will become less desirable. Data products should become broadly available to the astronomical community as a constituent of the multi-spectrum information accessible for research efforts.

International collaborations will play an increasingly important role in the construction and operation of gravitational wave observatories. Large collaborations which span the globe already play a vital role in the community, as readily evidenced by the existing networks of bar detectors and the emerging network of interferometric observatories. These networks facilitate the growth of technology, the sharing of expertise, and increase the capacity to pursue fundamental and large scale science initiatives. International networks will only continue to grow in the future of gravitational wave astronomy.

Over the next two decades, it is desirable to see undergraduate and graduate astronomy curricula evolve to include observational gravitational wave science as part of the suite of tools available to the modern astronomer. This is not a suggestion to inundate astronomy curricula with deep courses in general relativity, but to establish a curriculum which encompasses the fundamental science which can be learned from gravitational wave observations. This finding has been summarized by the mantra ``Less $G_{\mu\nu}$, more Rybicki & Lightman!''

Lastly, attention needs to be paid to Research and Development and budgets established to support emerging technologies. An agreed upon rule of thumb for R&D budgets in growing astronomical fields is $5-10\%$ of the total budgetary support in the field; estimates at the workshop suggested gravitational wave astronomy currently expends on order of $1-2\%$. Critical technologies which should bear scrutiny as we advance toward regular gravitational wave observations of the Universe are high power and high stability lasers, quantum non-demolition techniques, development of advanced materials, and computation and data analysis infrastructure.

A white paper summarizing the key findings and open debates left by the conference is in preparation, and will be posted to arxiv.org when it is completed. The program of the conference and the talks which were presented to encourage discussion have been posted online at the Center for Gravitational Wave Physics at Penn State, linked at

http://cgwp.gravity.psu.edu/events/GWA/.

It was intended that this workshop would be only the first of many such discussions the community will have with itself over the next decade. We strongly encourage everyone to consider these initial findings and whether they agree or disagree with them, to carry on the discussions and debates with your colleagues and groups at your home institutions, and to participate in future strategic planning events like this.