The Effect of Atmospheric Drag on Satellite Orbits

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The Effect of Atmospheric Drag on Satellite Orbits

• 2 Sep. 2004
• Jinyoung Park

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Overview

• 1. Importance of satellite drag research
• 2. The effect of satellite drag during the
  Bastille Day event
• 3. Analysis of the KOMPSAT-1 drag
• during the Oct. Nov. 2003 event
• 4. Summary Further work

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Importance of satellite drag research

• Re-entry operations
• Maneuver planning,
• ground track maintenance
• Precise orbit determination
• Collision avoidance prediction
• Space object catalogue maintenance

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Re-entry operations

• Many objects decay
• during each maximum
• in the 11-year solar
• cycle. Fragments of
• large objects can
• cause risks on the
• ground.
• (ex) July 11,1979
• Skylab-1 re-enters
• over the Indian Ocean
• and Australia

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Ground-track maintenance, maneuver planning

• For most radar altimetry missions, a repeating
• ground-track should be maintained to within
• /- 1 km to allow a proper interpretation of
  the
• sea-level measurements
• The planning of the required maneuver depends on
• the orbital decay of the satellite.

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Precise Orbit Determination

• Applications
• Radar altimetry
• Gravity recovery
• Ground station positioning, ...
• Tracking systems
• Satellite Laser Ranging
• GPS (Global Position System)
• DORIS (Doppler Orbitography and
• Radiopositioning Integrated by Satellite)

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Scale factors and empirical accelerations
1. Computed orbit, integrated from initial state
based only on force models
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Scale factors and empirical accelerations
2. Tracking observations (SLR, GPS, DORIS) do not
match the computed orbit
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Scale factors and empirical accelerations
3. The modeled aerodynamic force is multiplied
with a scale factor, estimated from the data, so
that the computed orbit better matches the
observations
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2. The effect of satellite drag
during the Bastille Day event

• 1) Introduction
• 2) Scientific Motivation
• 3) data Methodology
• 4) Analysis of Observations
• 5) Conclusion

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1) Introduction

• atmospheric drag contributes the largest single
  uncertainty to RSOs position determination and
  prediction.
• The density fluctuations under extreme conditions
  is significant.
• We derive a technique for extracting density
  measurements from orbit determination.

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2) Scientific Motivation

• drag retardation gt major influence on the
  dynamics of RSOs in LEO
• RSO drag measurements gt information about
  atmospheric density
• Drag measurements are sensitive to the total
  density over the path traveled by RSO.

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The bastille event time sequence

• a) On 7 July there was an Earth directed coronal
  mass ejection
• The disturbance from this event arrived on 10
  July.
• (not vigorous)
• b) On 11 July there was a high speed CME.
•     gt the disturbance arrived at 940 UT on 13
  July.
• c) On 14 July there was an X5 flare accompanied
  by another CME.
•     gt the disturbance arrived at 1900 UT on 15
  July.
• - The F10.7 index continued to be elevated for a
  period of about ten days as a result of enhanced
  emission from bright active regions.

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3) data Methodology

• Data
• 1. for a limited number of RSOs sensor
  observations -gt Naval Space Command
• 2. Element sets -gt entire catalog of
  approximately 8000 objects
• For this set, the orbital fit span used was
  in most cases three days.
• but, we used as short a fit span as possible
  in order to maximize sensitivity.

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• Model (to estimate the thermospheric density)
• 1. Jacchia 70 most widely used in the
• drag community.
• 2. MSISE-90 empirical model
• extensive, forty-year
  database
• 3. NRLMSISE-00 model
• an extensive database o total mass density

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Methodology the drag acceleration equation
drag coefficient
total density
direction unit vector

• aD CD A/M ½ r Vr2 u

area/mass ratio
relative velocity

• Total density is the most direct space weather
• parameter
• Composition and temperature determine
• aerodynamic interaction with the satellite
• Thermospheric winds influence relative velocity
  and direction of acceleration

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4) Analysis of Observations
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5) Conclusion

• Use of orbital for RSOs can provide significant
  information about thermospheric density
• the strong flare-associated enhancement of the
  F10.7 index on 12 July was not reflected in
  satellite drag
• The increase in RSOs drag on the 17th correlate
  well with the Ap and Dst indices, while both
  F10.7 and solc indices showed little change at
  this time
• We anticipate further progress using more
  physically-related quantities, such as UV airglow
  measurements of total mass density and solar EUV
  emission measures.

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3. Analysis of the KOMPSAT-1 drag during the
Oct. Nov. 2003 event

• The operational orbit evolution of the KOMSAT-1
  over 3 years was analyzed.
• The effects of unpredictable occurrence of the
  safe-hold mode and the highest solar activity on
  the orbit evolution during the mission life

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Solar Flux Satellite Drag
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Dst index Satellite Drag
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Ap Index Satellite Drag
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4. Summary Further work

• Importance of satellite drag research in space
  environment
• To use satellite drag measurements to provide
  information about atmospheric density
• The satellite drag correlates well with the Ap
  and Dst indices.
• Further work
• To analysis wide data of satellite drag and
  adroit IDLprogram (ex) interpolation

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