I can't wait to see the intermediary results. I am assuming the stray light problem is no longer an issue.
Anyone know if the summer 2016 release will have items such as the distance to the Hyades cluster & to standard candles like well known Cepheids so that metrics like the Hubble constant and stellar evolutionary models can be better calibrated?
First release: summer 2016 Potentially, the catalogue will be consisting of:- Positions (α, δ) and G-magnitudes for all stars with acceptable formal standard errors of positions. For this release, it is assumed that at least 90% of the sky can be covered. The release is for all objects with single-star behavior....
Second release: early 2017 Potentially, the catalogue will be consisting of:- Five-parameter astrometric solutions of objects with single-star behavior will be released under the assumption that at least 90% of the sky can be covered....
Thanks for that link. So no exo-planet list until 2022.
Any info on 1st catalog release date set in 2016?Any informed speculation?And finally what content would the 1st catalog contain?
ESA’s Gaia satellite is scanning the entire sky, detecting objects as faint as 20.7 magnitudes, but Planet Nine is likely to be fainter. Even if Gaia did see it, it probably would not be immediately recognized as a Solar System object, as its apparent motion (about 0.2 arcsecs per hour) is also below the current threshold for the Gaia data processing to immediately recognize it as a moving solar system object, but large enough to cause the planet to appear as a new “star” at a different position of the sky during subsequent Gaia observations. But Gaia might not need to see Planet Nine to find it.Like all massive objects, an otherwise invisible planet hiding in the outer reaches of the Solar System deforms the fabric of space-time around it, and the light from distant stars passing by the planet would be ever-so-slightly deflected. Measuring this deflection as the hidden planet passes in front of distant stars could reveal its presence, even if the planet itself is too faint to be seen. (See the animation below.) This temporary deflection is the less-well-known astrometric aspect of a phenomenon called microlensing, which also causes a temporary brightening of background sources (not shown in the animation).
Unfortunately it appears from their study that such a detection by Gaia is also unlikely. The expected deviation of a star’s direction for a 10 Earth mass planet at about 700 AU is incredibly tiny: about 3 milliarcsecs if the star is within 10 milliarcsecs of the planet’s position. (One milliarcsec is 1/1000 of an arcsecond, which is 1/3600 of a degree: That’s about the apparent height of Neil Armstrong standing on the Moon as seen from Earth.) Not only that, given the apparent motion of Planet Nine on the sky, such microlensing events would have a very short duration. Essentially a star would have to be within about 10 milliarcsecs of Planet Nine at the moment that Gaia observes it.Regardless of how Planet Nine is found (if it exists), measurements of microlensing events by the planet will likely be the only means to directly measure its mass, as any moons revolving around Planet Nine will be far too faint even for our most powerful telescopes. And while such microlensing events might be observable with other telescopes, only Gaia will be able to provide an accurate enough map of the sky to be able to accurately foresee such microlensing events.
The Gaia all-sky astrometric survey is challenged by several issues affecting the spacecraft stability. Amongst them, we find the focus evolution, straylight and basic angle variationsContrary to pre-launch expectations, the image quality is continuously evolving, during commissioning and the nominal mission. Payload decontaminations and wavefront sensor assisted refocuses have been carried out to recover optimum performance. An ESA-Airbus DS working group analysed the straylight and basic angle issues and worked on a detailed root cause analysis. In parallel, the Gaia scientists have also analysed the data, most notably comparing the BAM signal to global astrometric solutions, with remarkable agreement.In this contribution, a status review of these issues will be provided, with emphasis on the mitigation schemes and the lessons learned for future space missions where extreme stability is a key requirement.
The 24 hours period was later identified as an effect of the way the downlink is operated. Even though the phased array antenna is never switched-off, the signal coding scheme changed between ground station contacts (complex signal encoding only when downlink was active). This meant the transponders consumed more power during the contacts, which are typically scheduled according to a 24 hour logic. It was decided to force signal encoding without data transmission in the antenna outside contacts (except when spacecraft ranging is needed). This action reduced the impact of the 24 hours basic variation by more than half.
The correlation with the number of stars was puzzling at first glance, due to the negligible brightness of stellar sources. However, many service module components are affected by a bigger data rate, most notably the computers and the on-board data storage. A clear correlation thus exists between e.g. VPU5 and the peak basic angle variations, giving further support to the thermoelastic hypothesis.
Gaia isn't malfunctioning thermally is it?