ESA UNCLASSIFIED - For Official Use

Orbit Evolution of the Swarm Mission

Swarm Flight Dynamics Team

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 2

Content

Fuel consumption

Orbit evolution absolute

Altitude history and observed aerodynamic scale factors

Solar activity and altitude prediction (lower pair orbit raise)

RAAN/LTAN (orbit plane rotation)

Orbit plane difference (DLTAN) Swarm-B wrt lower pair

Lower pair separation

In-plane (Dsma, Dalong-track, Deccentricity, Daltitude)

Summary

Flight Dynamics activities

Outlook

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 3

Fuel Status

Available fuel:

EFIheating

Average

consumption:

0.8kg/y

60.359.8

63.2

A: 60.3 kg

C: 59.8 kg

B: 63.2 kg

Consumption can

increase at

stronger drag level

Dv =63m/s

MilBusFailHigh event

Safemode

zoom

InclinationChange

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 4

Fuel Status

Constellation maintenance manoeuvre

EFI TII cal

EFI TII cal

EFI TII cal

Di 0.159 kg

Di 0.968 kg

Di 1.030 kg

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 5

Altitude: Past Evolution

Semi major axis is calculated as osculating value at ascending node crossing

sem

i m

ajo

r axis

[km

]

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 6

Altitude Evolution, CD Value “Calibration”

Model of atmosphere:

NLRMSISE-00

Fixed average

spacecraft frontal

surface.

Orbit determination is

done with three day

arc. One drag

coefficient (CD) per

day is estimated.

CD=3.0

1.7

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 7

Altitude Evolution, Solar Activity PredictionD

ata

fro

m:

htt

ps:/

/sail.m

sfc

.nasa.g

ov/

Mean cycle obtained from averaging previous cycles

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 8

Altitude Evolution, Solar Activity PredictionD

ata

fro

m:

htt

ps:/

/sail.m

sfc

.nasa.g

ov/

Mean cycle obtained from averaging previous cycles

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 9

Altitude Evolution (Average Solar Cycle 25)Sem

i m

ajo

r axis

[km

](o

scula

ting a

t ascendin

g n

ode)

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 10

Altitude Evolution (Average Solar Cycle 25)

Dv 20m/s

Dv 15m/s

Dv 15m/s

Mar 2

02

2 Oct

2022

May 2

023

Sem

i m

ajo

r axis

[km

](o

scula

ting a

t ascendin

g n

ode)

Dv per s/c:~50m/s

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 11

Altitude EvolutionSem

i m

ajo

r axis

[km

](o

scula

ting a

t ascendin

g n

ode)

Mar 2

02

2

Same manoeuvres, but different cases ofsolar activity evolution

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 12

Orbital Plane Rotation

• WAC : ~8.3 deg/month

• WB : ~12.5 deg/month

.

.

Rate of change:

Full coverage (24h):• 8.8 months A/C

LTAN

RAAN

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 13

Orbital Plane Rotation

LTAN

RAAN

• WAC : ~8.3 deg/month

• WB : ~12.5 deg/month

.

.

Rate of change:

Full coverage (24h):• 8.8 months A/C

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 14

Orbital Plane Rotation

LTAN

RAAN

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 15

Content

Fuel consumption

Orbit evolution absolute

Altitude history and observed aerodynamic scale factors

Solar activity and altitude prediction (lower pair orbit raise)

RAAN/LTAN (orbit plane rotation)

Orbit plane difference (DLTAN) Swarm-B wrt lower pair

Lower pair separation

In-plane (Dsma, Dalong-track, Deccentricity, Daltitude)

Summary

Flight Dynamics activities

Outlook

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 16

Out-of-plane Evolution DLTAN

DLT

AN

[h]

LTANSwarm-C - Swarm-A

• Relative drift between B and lower pair: 0.13 h/month• Current difference: ~14.1 h – 12 h = 2.1 h

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 17

Out-of-plane Evolution DLTAN

Swarm-A: Δi=+15mdegSwarm-C: Δi= 0mdeg

1.9y

Oct.2019

3.Oct.2021Fuel: 2.2kg

11.Sep.2021

23.Oct.2021

DLT

AN

[h]

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 18

Content

Fuel consumption

Orbit evolution absolute

Altitude history and observed aerodynamic scale factors

Solar activity and altitude prediction (lower pair orbit raise)

RAAN/LTAN (orbit plane rotation)

Orbit plane difference (DLTAN) Swarm-B wrt lower pair

Lower pair separation

In-plane (Dsma, Dalong-track, Deccentricity, Daltitude)

Outlook

Flight Dynamics activities

Outlook

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 19

Lower Pair, Time Difference Along Track

Alo

ng t

rack t

ime d

iffe

rence [

s]

4s

10s

zoom

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 20

Lower Pair, Time Difference Along Track

Alo

ng t

rack t

ime d

iffe

rence [

s]

1xDi

6xDi

6xDi IP/IP

IPSwarm-A

IP Swarm-C

Swarm-A

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 21

Lower Pair, Average Altitude Separation

Swarm-C decay > Swarm-A Equal decay

60m

CAM

CurrentdecayA>C

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 22

Lower Pair, Altitude Separation

During the last month, Swarm-A decayed a bit faster than Swarm-C, in agreement with the predicted behaviour (different ballistic coefficient)

Sw

arm

-A –

Sw

arm

-Cdelta s

ma

[m]

11 Dec 2020Swarm-A manouvre

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 23

Lower Pair, Average Eccentricity Difference

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 24

Lower pair, Altitude Difference

Altitude difference at maximum latitude (close to crossing point of orbits).

Has to be kept small for collision avoidance in case of safe mode.

ESA UNCLASSIFIED - For Official Use Francesco Petrucciani | 26/05/2020 | Slide 25

Outlook

• More detailed study on lower pair orbit raise LTAN [h]

Latitu

des o

f clo

sest

overf

ly p

oin

ts

Upcoming activities:

The first batch of manoeuvres may need to start before March 2022

• Planning of operations to reach the lower pair configuration during the counter rotating orbit phase in Oct 2021

The desired configuration should to be achieved some months before.

Aug.2021 Oct.2021 Dec.2021