The Gaia satellite has just issued its most recent data release, the largest and most complete stellar census yet of our Galaxy, precipitating a virtual explosion of discovery in the world of astronomy. As I complete this article, dozens of articles have already posted on the open access online preprint archive astro-ph. This bounty of data is the fruit of many years of work on the part of over a thousand engineers and scientists. About half that effort was in the design, construction, launch and current operation of the Gaia satellite.

The other half, still ongoing, is a science consortium dedicated to transforming satellite telemetry into science products: the positions, motions, parallaxes and measured fluxes of well over a billion stars. Our view of the Milky Way will never be the same.

Some of the scientists currently involved in the data processing have worked on the Gaia mission their entire career, starting with formulating the initial concept proposal to the European Space Agency (ESA) some 20 years ago. For us long-term team members of the collaboration this data release is a culminating moment of our career. We are seeing our dream come true.

But I have to confess to some mixed feelings as well. As a result of their dedication, many of these starry-eyed dreamers have suffered delayed career advancement, as many academic and research institutes only measure scientific productivity via citable publications. Our institutes have given us the freedom to work on the mission and paid our salaries, but our time in Gaia is considered as scientifically non-productive. This continues to be a problem for young and old alike, because this mission still has years of data processing ahead of it.

There is another cutting-edge aspect of Gaia that sets it apart other space missions: its open data policy. Unlike other missions, there was practically no proprietary period given to Gaia scientists to preview the data and get a head start on the science. Yet many of us are involved in Gaia not because it was our dream to produce a billion-star catalogue, but because it was our dream to do science with a billion-star catalogue. It's great to see the science being done with Gaia data, and I love every discovery, but those now gathering the fruits of discovery are those who have had the time to prepare—time we’ve not had.

The argument has been made that we knew the rules of the game and that no one forced us to work on Gaia. True enough. But pursuing a science career already entails a financial sacrifice compared with our peers in other fields with similar expertise and preparation. Should choosing to work on a long-term science mission like Gaia entail an additional sacrifice?

In fact, a few of us did in fact have early data access, under “top-secret” conditions, to demonstrate the scientific potential of the new Gaia catalogue in the six performance-verification papers that accompanied the data release. I was one of those lucky few and I was painfully aware of my privileged status: Of the 20 or so people working on Gaia at my institute, I was the only one with early data access. Indeed, the line between the privileged and non-privileged team members was drawn across my office floor, which I share with another scientist who has been involved in Gaia as long as I have.

My early data access gave me an advantage with respect to my non-privileged colleagues, and raised a host of questions: Was this fair? Was this good for science? Was it good for Gaia? I could not help but notice that many of those who had invested and sacrificed as much as I for Gaia were not allowed to harvest the fruit of their labors.

Big science missions like Gaia take decades to be completed, and more than one generation is needed do so successfully. It is therefore essential that such missions attract and retain motivated and talented people. That cannot happen if those who invest their careers in such missions are not fairly rewarded.

I remain a fan of Gaia’s open data policy, because it's the best thing for science, but there is a painful incongruity between this policy and how science productivity is measured. A high price is being paid, not by ESA and the other space agencies who’ve financially invested in Gaia, but by the scientists working on the data processing, and it's a price measured in years.

Without taking a step back on open-data policies, we need to find a new way of doing business that fairly rewards scientists working in long-term science missions like Gaia, but all the players need to step up. In the case of Gaia here’s how we can do better:

Academic and research institutions need to broaden how they measure the productivity of their scientists. In today’s world full of big science, being a scientist often means more than doing research and writing papers. If institutions want to participate in big science, they need to reward the scientists who put their time in such projects.

The data processing consortium should create rather than limit opportunities for team members to publish papers, and should allow publications that are not strictly associated with data releases. It’s good for science, and it’s good for Gaia, because there is no better way to validate that we’re doing things right, and no better way to demonstrate Gaia’s future potential.

ESA should put more trust in the scientists that have invested their careers in the data processing. We all signed non-disclosure agreements, and we all know the consequences of leaking data outside the consortium.

If you’re working on Gaia data, think about inviting one or two Gaia experts in the collaboration—and not just the well-known Gaia scientists but also younger researchers who were involved with producing the data most critical to your project. Their contribution may be minimal, but their familiarity with the data is priceless. And it’s a nice way to say thanks.

It's great to see Gaia being lauded the world over, as it certainly deserves to be, and I can't help but feel immense satisfaction. All the effort and sacrifice has paid off because we are going to revolutionize astronomy with this mission.