HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

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Goddard Space Flight Center

mk_overview.ppt

Space Shuttle STS- 31 Deployment of HST on

April 25, 1990

AN EARLY STUDY OF DISPOSAL OPTIONS FOR THE HUBBLE SPACE TELESCOPE

Thomas Griffin, Scott Hull, Joy Bretthauer, Stephen LeeteNASA Goddard Space Flight Center

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

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LOGO.049

Goddard Space Flight Center

mk_overview.ppt

Purpose for the Study

Known Reentry Risk

– HST has no propulsion system; orbit is constantly decaying

– Uncontrolled reentry in 2040 +/- ~10 years

– Risk to the ground population is ~ 0.004 (about 1:250)

Disposal Options

– Controlled reentry is one obvious option to study

– Are there other disposal options available?

Study Topics

– Are there practical options to controlled reentry for the disposal of HST, and what are the costs and benefits to each in terms of risk to both the public and the shared orbital environment?

– What is the necessary schedule for successful disposal of HST?

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

3

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Goddard Space Flight Center

mk_overview.ppt

Wide Field Planetary Camera 2COSTARGyrosSolar Arrays

Launch!

Imaging SpectrographNear Infrared CameraFine Guidance Sensor

GyrosAdvanced ComputerFine Guidance Sensor

Advanced CameraSolar ArraysPower Control UnitNICMOS Cooling System

GyrosWide Field Camera 3Cosmic Origins SpectrographBatteriesFine Guidance SensorSTIS RepairACS RepairNew Outer Blanket LayerSoft Capture Mechanism

SM1

SM2

SM3A

SM3B

SM4 DisposalMission

Hubble Servicing Missions

Hubble Servicing Missions

1990 1993 1997 1999 2002 2009 ~2024 3

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

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Goddard Space Flight Center

mk_overview.ppt

NASA / ESA Partnership

NASA and ESA have been partners in HST for over 30 years

Together, ESA and NASA have forged a four decade long Partnership that has revolutionized the Astronomy Community.

Original ESA/NASA HST Memorandum of Understanding was signed in 1977

This relationship will continue through the Disposal of the Observatory

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

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Goddard Space Flight Center

mk_overview.ppt

HRSDM Foundations and Lessons

In March 2004, a design effort was undertaken to perform the Hubble Robotic Servicing and De-orbit Mission (HRSDM)

Within one year, a full mission was designed through PDR

– Rendezvous and capture HST

– Change out two science instruments and spacecraft bus hardware

– Detach Servicing Module, leaving the Deorbit Module on HST

– Controlled reentry some years later

Much of the background research and planning is still applicable

– Tumble rates

– Rendezvous and capture techniques

– Propulsion system sizing

This effort spawned the current Satellite Servicing efforts at GSFC

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

6

LOGO.049

Goddard Space Flight Center

mk_overview.ppt

Orbit Decay Profile for HST

HST tumble rates are acceptable above 500 km

Earliest credible date for reaching 500 km is 2024

Disposal decisions do not need to be made immediately

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

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Goddard Space Flight Center

mk_overview.ppt

Orbit Change Options Considered

Drag Enhancement

– Can accelerate the reentry of HST

– Insufficient control to positively determine the reentry location

– Methods included balloon, mist, sail, tether

Laser Nudging

– Insufficient thrust to make substantial orbit changes

Intentional Breakup

– Makes the reentry risk worse unless all resulting particles are very small

Propulsion

– Chemical propulsion – monopropellant and bipropellant

– Electric propulsion

– Electrodynamic tether

– All are feasible, and have potential applications for HST disposal

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

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Goddard Space Flight Center

mk_overview.ppt

Disposal Options Considered

Option 1: Controlled Reentry

– Bipropellant propulsion to 50 km perigee and ocean reentry

– Removal from orbit at least 6-10 years before natural decay

– High profile event, with great consequences for anomalies

Option 2: Boost to 1200 km

– Highest practical altitude for chemicalpropulsion

– Very low existing debris density

– Long-term stable orbit

– Incompatible with existing guidelines

Option 3: Boost to 2000 km

– Electric propulsion or electrodynamic tether

– Longer time to reach the final orbit

– Naturally circular resulting orbit, meets existing guidelines

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

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Goddard Space Flight Center

mk_overview.ppt

Feasible Options Identified

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

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Goddard Space Flight Center

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Collision Risks (>10 cm)

Inherent Collision Risks

– Since launch, HST has accumulated ~0.00200

– By 2024, risk estimated as 0.00300

Option 1: Controlled Reentry

– Additional large object risk is zero

Option 2: Boost to 1200 km

– Risk during orbit raising is near zero, including conjunction assessment

– Collision risk during storage estimated as ~0.00007 per year

Option 3: Boost to 2000 km

– Risk during orbit raising is near zero, including conjunction assessment

– Collision risk during storage estimated as ~0.00001 per year

Collision risks estimated using DAS 2.0.2 (ORDEM2000)

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Sixth European Conference on Space Debris

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Reentry Risks

Do Nothing: Uncontrolled Reentry

– Reentry risk is estimated as 0.004323 for reentry in 2031 (1:230)

Option 1: Controlled Reentry

– If successful, reentry risk is zero

– End-to-end risk is 0.000111 (1:9000), 39X reduction in overall risk

Option 2: Boost to 1200 km

– If successful, reentry risk is zero

– End-to-end risk is 0.000111 (1:9000), 39X reduction in overall risk

Option 3: Boost to 2000 km

– If successful, reentry risk is zero

– End-to-end risk is 0.000376 (1:2650), 11.5X reduction in overall risk

End-to-end risks include the reliability of the launch, rendezvous, and orbit change

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

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Conclusions

There are feasible disposal options for HST, in addition to controlled reentry

Each of the disposal options carries a different set of advantages, disadvantages, and challenges

Drag enhancement, intentional breakup, and laser nudging were all found to be impractical approaches for the disposal of HST

A decision on the ultimate HST disposal method and design can be delayed at least five years without reducing its success

Disposal Option Advantages DisadvantagesUncontrolled Reentry Zero cost Unacceptable public risk1) Controlled Reentry Lowest cost, Short time

Meets all disposal requirementsMature technologyAccepted approach

Sensitive to errorsHigh visibility

2) Boost to 1200 km Short timeLow costInsensitive to errors

Violates NASA requirements and International agreements

Higher collision risk3) Boost to 2000 km Meets all disposal requirements

Insensitive to errorsLongest timeHighest costTechnology maturity

HUBBLE SPACE TELESCOPE PROGRAM

Sixth European Conference on Space Debris

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Questions

Please feel free to email questions to

Scott.Hull@NASA.gov