IBEX Mission Planning and Operations

Mike LoucksSpace Exploration Engineeringloucks@see.com360-378-7168

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Interstellar boundary explorer science objectives

Discover the global interaction between the solar wind and the interstellar medium

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The IBEX orbit

Science above the Geotail

Dump data at low altitudes

Orbit highly perturbed by Lunar gravity

Must avoid:– Re-entry– Long shadows

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The IBEX flight dynamics team:thing 1, thing 2: ODTK and STK

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IBEX spacecraft

Spinner Integrated Propulsion System for Orbit Raising +/- Z Thrusters

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IBEX orbit raising

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IBEX flight dynamics requirements: mission analysis

For a given launch date, identify a final orbit that:

– Has a desirable perigee history over 6 months Above 7000 most of the time Below 30,000 most of the time

– Has no shadow durations that are excessive ½ Penumbra + umbra duration < 4.0 hours

Target back to this orbit for range of +/- 3 sigma SRM dispersions for a given launch day

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Prelaunch mission analysis: STK/Astrogator

2-year Perigee Altitude History

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Prelaunch mission analysis: STK/Astrogator

Nominal Screened Orbit: 2-year Shadow History

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IBEX ascent: correcting launch errors

3 Sigma Low, Nominal, 3 Sigma High SRM Burns

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Mission analysis: planning and operations Monte Carlos

LEOPS Monte Carlo

– Start with Nominal Covariance and state vector from baseline OD process

– Each successive maneuver targeted, saved and then errors introduced along with statistical state errors based on covariance

– Product of this process is nominal state vector at end of LEOPS and covariance

Long-term Monte Carlo

– Start with Covariance from LEOPS Monte Carlo and state vector

– Single state run

– Hyper-cube scan

– Full Monte Carlo (10,000 runs) based on covariance

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IBEX nominal orbit raising plan

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Operations, post AM1: requirements changed!

Radiation concerns cause nominal perigee altitude to be adjusted. Desire to stay between 1 and 3 Re.

Aim for 5 year lifetime (without maneuvers) if possible

Re-Plan final orbit “On the fly”– 4 laptop computers running Excel/STK monte-carlos

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Operations: post AM1 orbit raising plan

Catalog “A”, P4 Altitude Raised by Moon at A4

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Operations: post PM1

10% under-burn – Neutralizes Lunar perturbations at A4– Requires extra DV at AM2, and burn in excess of 600 sec– AM2 moved up 1 rev, AM3 added

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Operations: post PM1

AM2 Plan

– Max burn planned for 600 sec

– Discovered that 614 sec burn (114 m/sec) DV gives viable new Catalog orbit (found another one)!

– Any burn within +5% or -10% also works

– Performance within this range and: We’re done!

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Operations: final ascent

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Operations: final orbit

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Final catalog: shadow event durations

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AGI technology and IBEX

STK/Astrogator– All pre-mission planning and operations performed

with Astrogator and MS Excel. Thousands of monte-carlo runs

Orbit Determination Tool Kit– All pre-mission and operational navigation planning

performed with ODTK All operational tracking and maneuver reconstruction

performed with ODTK and scripting tool Debugging and characterization of hardware in real time ops

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Results

STK and ODTK complete navigation solution brought in post-PDR

Scripting interface allowed rapid prototyping and development

Stability and flexibility of platform allowed risk mitigation via monte-carlo analysis.

Physics-based ODTK solution allowed debugging of hardware

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Summary

Mission duration extended x2 during operations

Completely re-planned ascent and final orbit during ops

Pre-launch training with all tools very important

Flexibility of tools and personnel was key