Posted by Nick James at 00:28 on 2013 Dec 22
I managed to observe Gaia again tonight between rain and gales but it is dramatically fainter than a couple of nights ago at around mag 17.6. It is also about three arcmins SW of the position predicted. I assume that the magnitude change is due to a change in the spacecraft attitude so that the sunshade is now offset but I need to confirm this.At present it is around 400,000km away so it will be around 3 mags fainter at L2.Nick.Update at 08:37, Dec 22 – The Gaia optical tracking team have confirmed that the reason for the dramatic fade (a factor of a around 100) is a change of spacecraft aspect angle. The large reflective sunshade is now angled at about 45 deg to our line of sight. There’s an interesting paper on this here. This is the final aspect angle that the spacecraft will have at L2.