# CAPSTONE mission

#### Ajaja

##### Active member
HORIZONS says "Data through Oct 23, predictions thereafter"
I think everything after Oct 23 is just calculated ballistics without corrections.

#### BrianJ

Hi,
HORIZONS says "Data through Oct 23, predictions thereafter"
I think everything after Oct 23 is just calculated ballistics without corrections.
I'm not so sure - if you look at Horizons data the aposelene goes from 205681km to 97714km during 18mins around periselene, on 13 November 2022. That doesn't happen in Orbiter without a burn.

Looks fine.
For example, if you try to propagate backward from 14 Dec 2022 there is the trajectory:
Nice image - what are you using? GMAT?
What happens if you propagate forward? I'd guess you get the same as me in Orbiter - Capstone starts to escape lunar orbit.

Looks like the orbit is more-or-less stable for 30 days, then starts to unravel. I guess I was expecting longer term stability and a more consistent orbit plane relative to Earth-Moon line.

I made a scenario for 14 Nov 06:00UTC (about 6 hours after LOI), here's a 3-view plot from LagrangeMFD (Earth-Moon rotating frame) for 30 days from 14 Nov-14 Dec. Concurs with your image pretty much, and I think you can see the orbit starting to drift at the end.

I would think there needs to be a correction burn before 14 Dec.
At least I have an idea of what an NRHO looks like on LagrangeMFD now!
Cheers,
Brian

#### Ajaja

##### Active member
Yes, I used GMAT.
And yes, according to GMAT as well as Orbiter CAPSTONE with this POS/VEL from HORIZONS escapes Moon just soon after 14 Dec. Moreover, it looks like it's already way off NRHO, so I think there should be corrections before this date (and after 14 Nov) which were not included in HORIZONS data. Maybe they are not scheduled yet.

Last edited:

#### BrianJ

Yes, I used GMAT.
And yes, according to GMAT as well as Orbiter CAPSTONE with this POS/VEL from HORIZONS escapes Moon just soon after 14 Dec. Moreover, it looks like it's already way off NRHO, so I think there should be corrections before this date (and after 14 Nov) which were not included in HORIZONS data. Maybe they are not scheduled yet.
I think you must be right. So maybe we'll see a more stable/finely tuned NRHO shown in the Horizons data shortly.

#### Ajaja

##### Active member
Yes, I can confirm, there are course corrections before Nov 14-15, but after that it's ballistics.
I was even able to find some parameters for solar radiation pressure model to get almost the same POS/VEL after propagating Nov 15 - Dec 14:
HORIZONS (Moon body center, Ecliptic of J2000.0 ):
Code:
2459927.500000000, A.D. 2022-Dec-14 00:00:00.0000, -3.540615979107255E+04,  1.054132688459846E+04, -4.928965709311910E+04, -3.865808101214649E-02,  7.819699210330527E-02, -2.120745164618341E-01,
GMAT:
Code:
TDB Epoch:    14 Dec 2022 00:00:00.000
Cartesian State
---------------------------
X  =  -35406.854827069 km
Y  =   10541.648590011 km
Z  =  -49289.027182366 km
VX =  -0.0386621288764 km/sec
VY =   0.0781966607821 km/sec
VZ =  -0.2120764223620 km/sec

BTW, solar radiation pressure makes a significant difference for a such tiny spacecraft.

#### Ajaja

##### Active member
BTW, they have removed the data after Nov 14 from Horizons.
Now it's only:

#### Gargantua2024

##### The Desktop Orbinaut
Probably only temporary as the day of lunar orbit insertion nears to provide real trajectory data based on its performance

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