Strictly speaking, to get the optimum results in intereforometry, the satellite orbits should be the same. The limitation of this is that only one surface displacement vector can be resolved. So, many studies carried out using both ascending and descending orbits to isolate vertical from horizontal motion. have a look on these articles.
You can collect a few images derived by both ascending and descending orbits and do the interferometric processing and see what you get.
Your graph looks correct