Mentor 10 (USA 353), the NROL-70 payload, likely found near 98 E [UPDATED]

click image to enlarge. Image (c) by @mickeywzx, used with permission

It appears that Mentor 10 (USA 353), the payload of NROL-70, which launched on 9 April 2024 at 16:53 UTC, has been found on orbit by Twitter user @mickeyWZX (Zhuo-Xiao Wang) who is located at Baihuashan Observatory (MPC code P13) in the suburbs of Beijing. 

It is a bright object, reportedly about mag. +7.6, which conforms to the expectation of an ADVANCED ORION, a SIGINT satellite class known as 'Mentor' among independent trackers. These objects are the largest and brightest geosynchronous satellites in the sky with a typical observed brightness near mag +8 (see my 2016 article in The Space Review that discusses one of them as part of a larger story).

When found on April 11, two days after launch, it was located near longitude 97 E.

 A preliminary TLE which the observer posted on Twitter suggests it is drifting westwards in longitude at 0.6 deg/day, indicating it was originally inserted at 98.0 E. 

[update] a TLE over an arc of several days suggests it is drifting westwards in longitude at ~1.3 degrees/day, indicating it was originally inserted at 100.3 E. [/update]

That is basically in agreement with my pre-launch estimate (100 E), but the orbital inclination of 8 degrees is a bit higher than my estimated 5 degrees. Still, the resemblance to my pre-launch estimate is good.

 

click to enlarge

 

In the map below, my pre-launch estimated insertion orbit is depicted (blue) along with the orbital track of the payload after insertion (yellow), from April 9 22:45 UTC to April 19 12:00 UTC (note the daily analemma caused by the 8 degree orbital inclination). The yellow crosses give positions for various future dates if the current drift of 12.3 deg/day westwards continues:

Click map to enlarge

At this moment, the payload is probably controlled from Pine Gap Joint Defense Facility in Australia. If it continues to drift westwards, RAF Menwith Hill in the UK might at some point take over. 

At the current drift rate, if it continues this way, it should become visible at sufficient sky elevation from my location by late May 2024. 

It will be interesting to see where the drift stops. My guess, based on current hightened interest in what is going on in Ukraine, Gaza and the Red Sea area, is somewhere near 30 E. But who knows: it might go as far as 15 W, based on historic positions for this line of satellites.

A preliminary TLE based on observations by @mickeywzx [updated]:

Mentor 10
1 59453U 24067A   24109.01742676 0.00000000  00000-0  00000+0 0    06
2 59453   7.9821 302.0687 0008030 158.5115 201.5250  0.99896432    03

 

(I thank @mickeywzx for allowing the use of his photography in this post)