Some more manual approach and docking practice today!
Here’s a closer look at the instruments we use. I have talked in the L-352 Logbook about the periscope view, which is oriented forward when we approach the Station. In the picture you can see the view when the Soyuz has docked: the romboidal target is aligned with the periscope and we need to keep it in the center with the crosses aligned. In this particular docking, if you look carefully, you can see a minor misalignment in pitch (the horizontal line is a bit low), which is still fully acceptable.
The big challenge in flying manually is that we don’t have measurements of distance and speed. We assess the distance visually using the grid and a conversion table based on the apparent dimension of the Service Module, the docking port and the target. For example, we know that when the Service Module diameter is as wide as 1 grid division we are at 200 meters; if the diameter of the docking port is 2 divisions, we are at 70 meters; and if the target is 3 divisions, we are at about 3 meters from contact.
Speed assessment is a bit trickier and is based on the known acceleration of the thrusters. If we start from a closing speed of roughly zero and give a forward impulse of 10 seconds, we know that we have accelerated to about 0,4 meters per second. It gets more difficult in computer failure scenarios, because any time we use the orientation control on the right to adjust pitch or yaw, we also give a significant burn forward which is not compensated and needs to be accounted for. It’s especially important when we make contact with Station: we want the speed to be between 0.06 m/s and 0,15 m/s. Especially not higher than that!
(Trad IT) Traduzione in italiano a cura di +AstronautiNEWS qui:
https://www.astronautinews.it/tag/logbook/
(Trad ES) Tradducción en español aquí:
https://www.intervidia.com/category/bitacora/
(Trad FR) Traduction en français par +Anne Cpamoa ici:
https://anne.cpamoa.free.fr/blog/index.php/category/logbook-samantha
11/12/2013