ASEN 5335 - Aerospace Environment -- Orbital Debris 1 Coronal holes and Solar wind speed and density The interplay between the inward pointing gravity

ASEN 5335 - Aerospace Environment -- Orbital Debris 1

Coronal holes and Solar wind speed and density

The interplay between the inward pointing gravity and outward pointing pressure gradient force results in a rapid outward expansion of the coronal plasma along the open magnetic field lines.

At low latitudes the direction of the coronal magnetic field is far from radial. Therefore the plasma cannot leave the vicinity of the Sun along magnetic field lines. At the base of low-latitude coronal holes, however, the magnetic field direction is not far from radial, and the expansion of the hot plamsa can take place along open magnetic field lines without much resistence fast solar wind.


Coronal Holes

One of the major discoveries of the Skylab mission was the observation of extended dark coronal region in X-ray solar images. These coronal holes are characterized by low density cold plasma (about half a million degrees colder than in the bright coronal regions) and unipolar magnetic fields (connected to the magnetic field lines extending to the distant interplanetary space, or open field lines). The figure on the right is from recent Yohkoh s/c.

Near solar minimum coronal holes cover about 20% of the solar surface. The polar coronal holes are essentially permanent features, whereas the lower latitude holes only last for several solar rotations.


The first x-ray images > 30 keV have been obtained with the hard X-ray Telescope on the Yohkoh satellite.

The relationship between the nonthermal (accelerated) electrons and the hottest thermal electrons can be studied by observing the time evolution of both components during a flare. Likewise, the relationship between these energetic components and somewhat cooler thermal plasma can be studied by comparing the hard x-ray observations with the evolution of the soft x-ray emission.


Solar Cycle

Our ever changing Sunover its 11 year cycle - seen here in X-rays


The wavelengths most significant for the space environment are X-rays, EUV andradio waves. Although these wavelengths contributeonly about 1% of the total energy radiated, energy at these wavelengths is mostvariable


SOME CONTRIBUTIONS OF HELIOSEISMOLOGY

• Convection zone deeper (R=0.71) than previously thought.

• Limits set on the abundance ofHelium in convection zone.

• Rotation rate of the convection zone is similar to that of surface.

• Near the convection zone base, rotation rate near the equator decreases with depth, and rotation rate at high latitudes increases with depth, so that the outer radiation zone is rotating at a constant intermediate rate.



“Halo CME”


Electron density 7.1 cm-3 Proton density 6.6 cm-3

He2+ density 0.25 cm-3 Flow speed 425 kms-1

Magnetic field 6.0 nT Proton temperature 1.2 x105 K

Electron temperature 1.4 x105 K

Observed Properties of the Solar Wind at 1 AU

The pressure in an ionized gas with equal proton and electron densities is

Pgas = nk (Tp + Te)

where k is the Boltzmann constant, 1.3807x10-23 JK-1, and Tp and Te are proton and electron temperatures. Thus,

Pgas = 2.5 x 10-10 dyn cm-2 = 25 pico pascals (pPa)

Similarly, a number of other solar wind properties can be derived (see following table)

Derived Properties of the Solar Wind


THE INTERPLANETARY MEDIUM AND IMF

Intermixed with the streaming solar wind is a weak magnetic field, the IMF.

The solar wind is a “high-” plasma, sothe IMF is "frozen in”;the IMF goes wherethe plasma goes.

Consequently, the "spiral" pattern formed by particles spewing from a rotating sun is also manifested in the IMF. The field winds up becauseof the rotation of the sun. Fields in a low speed wind will be more wound up than those in high speed wind.


Loci of a succession of fluid particles emitted at constant speed from a source fixed on the rotating Sun.

Loci of a successionof fluid parcels (eightof them in this sketch)emitted at a constantspeed from a sourcefixed on the rotatingSun.


IMF as a function of the distance The following equations shows the IMF as a function of r. The radial and azimuthal component of the IMF behave quite differently.

The radial component decreases with r-2, whereas the azimuthal component decreases only as r-1. Thus as going outward, the magnetic field becomes more and more azimuthal (it “wraps around”) in the equatorial plane.

At the same time the field behaves quite differently over the solar polar regions.


Heliosphere, a schematic view

Note that IMF is dominated by the azimuthal component at large distance, while the solar wind flow is always dominated by the radial component.


Coronal holes and Solar wind speed and density

The interplay between the inward pointing gravity and outward pointing pressure gradient force results in a rapid outward expansion of the coronal plasma along the open magnetic field lines.

At low latitudes the direction of the coronal magnetic field is far from radial. Therefore the plasma cannot leave the vicinity of the Sun along magnetic field lines. At the base of low-latitude coronal holes, however, the magnetic field direction is not far from radial, and the expansion of the hot plamsa can take place along open magnetic field lines without much resistence fast solar wind.



> 700 keV ions and > 500 keV electrons



> 20 MeV Ions (most protons)


SAMPEX measured Anomalous Cosmic Ray Particles (Oxygen Nuclei, >200 keV/nucl)


As the magnetized solar wind flows past the Earth, the plasma interacts with Earth’s magnetic field and confines the field to a

cavity, the magnetosphere.


(Temerin and Li , 2002)

Prediction efficiency=91%

Linear correlation coeff.=0.95



Review of Charged Particle Motions

• Gyromotion motion: =p2/2mB (1st), T_g~10-3 sec

• Bounce Motion: J= p||ds (2nd), T_b~100 sec • Drift motion: =BdA (3th) , T_d~103 sec


Loss Cone and Pitch Angle Distribution

Obviously this will happen if eq is too small, because that then requires a relatively large BM (|B| at the mirror point).

The equatorial pitch angles that will be lost to the atmosphere at the next bounce define the loss cone, which will be seen as a depletion within the pitch angle distribution.

B

losscone

Particles will be lost if they encounter the atmosphere before the mirror point.


The core motions are induced and controlled by convection and rotation (Coriolis force). However, the relative importance of the various possible driving forces for the convection remains unknown:

• heating by decay of radioactive elements

• latent heat release as the core solidifies

• loss of gravitational energy as metals solidify and migrate inward and lighter materials migrate to outer reaches of liquid core.

Venus does not have a significant magnetic field although its coreiron content is thought to be similar to that of the Earth.

Venus's rotation period of 243 Earth days is just too slow to produce the dynamo effect.

Mars may once have had a dynamo field, but now its most prominentmagnetic characteristic centers around the magnetic anomalies inIts Southern Hemisphere (see following slides).


Aerospace EnvironmentASEN-5335

• Instructor: Prof. Xinlin Li (pronounce: Shinlyn Lee)

• Contact info: e-mail: [email protected] (preferred)

phone: 2-3514, or 5-0523, fax: 2-6444,

website: http://lasp.colorado.edu/~lix

• TA’s office hours: 9-11 am and 3:15-5:15 pm Wed at ECAE 166 for this and next week.

• Guest Lectures next week: Terry Onsager on 4/8 and David Klaus on 4/10.

• Quiz-6, 4/15 (Tue), about radiation and other effects on s/c and human beings; and space Debris.

• HW5 due 4/3 (Thu) and HW6 due 4/17 (Thu)

mailto:[email protected]

http://lasp.colorado.edu/~lix


Earth’s Orbital Debris Environment

• Over 9,000 objects in Earth orbit are currently tracked

• An unknown number of undetectable objects of various sizes are known to exist

• Earth’s atmosphere is bombarded

by tons of meteoric material daily• What are the hazards ?

LEO

GEO




This is the impact crater on the number 5 window of the Space Shuttle Challenger. Occurred June, 1983, on the STS 7 mission. Affected area is about 0.5 cm diameter. Impacting particle was a 0.2 mm fleck of white paint of the same type used to paint Delta upper stages. Models suggest relative speed of 3-6 km/s at impact.

A Debris Example(Courtesy of Prof. R. Culp of ASEN)


Space Junk:

What is the Potential Damage?

Size of Object Damage

• Less than 1/250 inch surface erosion

• Less than 1/25 inch possible serious damage

• 1/8 inch ball traveling at Like a bowling ball

22,000 mph traveling @ 60 mph;

(bad)

• 1/2 inch aluminum ball Like a 400-lb safe

traveling at 22,000 mph traveling @ 60 mph;

(nasty)


References

• Johnson, N.L., and D.S. McKnight, Artificial Space Debris, Orbit Book Co., Malabar, Florida, 1991.

• History of on-orbit satellite fragmentations, Orbital debris program office, N. Johnson et al., NASA Johnson Space Center, JSC 29517, LMSEAT33746, July, 2001.

• The new NASA orbital debris engineering model ORDEM2002, J-C Liou et al., NASA/TP-2002-210780, May, 2002.

• http://www.orbitaldebris.jsc.nasa.gov/

• http://www.aero.org/cords

• http://www.wstf.nasa.gov/Hazard/Hyper


Orbit Categorizations

LEO GEO


Space Debris Overview

• Originate from comets, asteroids• 200 kg of mass within 2000 km• Largest flux below size of 0.5 mm• Low densities & mass;

(0.1-0.5 g cm-3)• High velocity - avg 19 km s-1

• Flux steady with time• Affected slightly by solar cycle• Quasi-isotropic flux (some Earth

shielding factor)

• > 9000 large enough to be tracked

• 1.5-3.0 x 106 kg within 2000 km

• Largest flux above size of 1 mm

• Higher densities & mass;

(2-9 g cm-3)

• Lower velocity – 8 -- 10 km s-1

• Flux increasing with time

• Affected by launch rate, launch operations, solar cycle

• Majority in high-use orbits

Natural Debris Artificial Debris


Factors Affecting Satellite Population

Satellite Population

Launch andOperations Activity

SatelliteDeteriorations

Satellite Fragmentations

Retrievaland Deorbits

OrbitalDecay

SINKS

SOURCES

Atmospheric DragSolar-Lunar PerturbationsRadiation Pressure

Launch rateRocket StagesLoose Hardware

Atomic oxygenSolar Radiation

DeliberateAccidental/PropulsionCollisionUnknown


Overview of Artificial Debris Population

Primary factors affectingsatellite population

• launch rate• satellite fragmentations• solar activity

Projection primarily based on 1992-1999 traffic


Ten of more than 4150 space missions flown since 1957 account for 21% of all catalogued satellites in orbit as of May 2001

All but one are discarded rocket bodies

• The majority of detectable fragmentation debris have already fallen out of orbit• The effects of 45% of all fragmentations have disappeared


Satellite Fragmentations

• Fragmentation Debris -- destructive disassociation of an orbital payload, rocket body or structure -- wide range of ejecta velocities

• Anomalous Debris -- result from unplanned separation of object(s) from a satellite which remains intact, i.e., deterioration of thermal blankets, protective shields, solar panels -- low relative velocities

• Operational (Mission-Related) Debris -- ejected during deployment, activiation, de-orbit of payloads, manned operations, etc.

Relative segments ofthe catalogued in-orbitsatellite population


Debris Type vs. Orbit Accounting, 30 May 2001


Debris Source vs. Type Accounting, 30 May 2001


Debris Source vs. Orbit Accounting, 30 May 2001


U.S. Space Surveillance Network

Dedicated -- USSPACECOM primary spacetrack missionCollateral -- USSPACECOM

other primary missionContributing -- controlled by non-

USSPACECOM NE -- near EarthDS -- deep space

What are the data sources ?


Measurements of near-Earth orbital debris is accomplished by conducting ground-based and space-based measurements of the orbital debris environment. Data is acquired using ground-based radars and telescopes, space-based telescopes, and analysis of spacecraft surfaces returned from space. The data provide validation of the environment models and identify the presence of new sources.

Orbital Debris Measurements

Optical Measurements Radar Measurements

http://www.orbitaldebris.jsc.nasa.gov/measure/radar.html

http://www.orbitaldebris.jsc.nasa.gov/measure/optical.html

http://www.orbitaldebris.jsc.nasa.gov/measure/msx.html

http://www-curator.jsc.nasa.gov/curator/seh/seh.htm


Representative US SSN Coverage at 400 km altitude

For fragmentations belowabout 400 km, much of thedebris may reenter beforedetection, identification &cataloging can be completed Red: optical

Blue: radar

• At low altitudes (<2000 km) cataloged debris are larger than ~10 cm in diameter

• At higher altitudes objects less than ~1m in diameter may be undetectable

• Need for detection of smaller debris (<10 cm) in most of space


The space object environment is usually described in terms of a spatial density [1/km3] that represents an effective number of spacecraft and other objects as a function of altitude (i.e., an object in circular orbit represents much more of a collision hazard than one that occasionally traverses this region)

The geosynchronous altitude population, 28 May 2001

GPS/Glonass Spacecraft

Higher-altitude near-Earth and general deep-space populations


Near-Earth (100-2000 km) population, 28 May 2001

Linear scale

Log scale

ORBCOMMConstellationIRIDIUM

Constellation

OPS-4682SNAPSHOTSpacecraft

Note: fragmentationdebris often dominate


Satellite Fragmentations during the 1990’s

1 Jan 2000

Areas of bubbles proportional to number of debris created by a specific event

• 55 explosions and the first recorded unintentional collision occurred during the 1990’s


Satellite Breakups

Proportion of all cataloged satellite breakup debris

Number of breakups by year since 1957

• The most important category of on-orbit debris

• Account for 38% of the existing satellite population

• 170 satellites have broken up since 1961

• Primary causes are deliberate actions & propulsion-related events


Aerospace EnvironmentASEN-5335

• Instructor: Prof. Xinlin Li (pronounce: Shinlyn Lee)

• Contact info: e-mail: [email protected] (preferred)

phone: 2-3514, or 5-0523, fax: 2-6444,

website: http://lasp.colorado.edu/~lix

• TA’s office hours: 9-11 am and 3:15-5:15 pm Wed at ECAE 166 for next week.

• Guest Lectures next week: Terry Onsager on 4/8 and David Klaus on 4/10.

• Quiz-6, 4/15 (Tue), about radiation and other effects on s/c and human beings; and space Debris.

• HW5 due today and HW6 due 4/17 (Thu)

mailto:[email protected]

http://lasp.colorado.edu/~lix


The space object environment is usually described in terms of a spatial density [1/km3] that represents an effective number of spacecraft and other objects as a function of altitude (i.e., an object in circular orbit represents much more of a collision hazard than one that occasionally traverses this region)

GPS/Glonass Spacecraft

Higher-altitude near-Earth and general deep-space populations

Anomalous Debris -- result from unplanned separation of object(s) from a satellite which remains intact, i.e., deterioration of thermal blankets, protective shields, solar panels -- low relative velocities


• Overview of Debris Population

• Natural vs. Artificial Debris

• Debris Sources and Sinks

• Characterization of the Debris Environment

– Detection, tracking, surveillance

– Impact characterization (Gabbard diagrams)

– Modeling the environment

• Long Duration Exposure Facility (LDEF)

• Future Trends/Mitigation Strategies

Earth’s Orbital Debris Environment


IMPACT CHARACTERIZATION• Brief review of orbital perturbations• Gabbard Diagrams

posigradeimpulse

original orbit

final orbit

Semi-major axis & period increase

final orbit

original orbit

retrogradeimpulse

Semi-major axis & period decrease

At perigee: posigrade/retrogradewill raise/lower apogee

At apogee: posigrade/retrogradewill raise/lower perigee

Radial impulseapogee, perigee change

semi-major axis & period almost unchanged

Out-of-plane () impulselittle change


Gabbard Diagrams

+

+

circular orbit

elliptical orbit

Single-satellite Gabbard diagrams

• Depict apogee, perigee, and period of orbiting objects• Used to infer information about fragmentation events


1973-086B

+

Gabbard diagram for debris from breakup of satellite 1973-086B

same apogees

diff

eren

t per

igee

sThese fragments received a net retrograde impulse

from the breakup

These fragments received a net

posigrade impulse from the breakup

diff

eren

t apo

gees

same perigees

initially circular

orbit

Note: retrograde pieceshave apogee altitudessimilar to the perigeesof the posigrade pieces.

This follows from the impulse maneuver analogies: An impulse at perigee (apogee) does not affect perigee (apogee) height, but only changes the apogee (perigee) height. For a circular orbit, apogees and perigees are defined once the impulse occurs


1971-015A

+

Gabbard diagram for breakup of a satellite in elliptical orbit

mostly

retrograde impulse

Same perigee height; therefore,fragmentation occurred near perigee

Range of apogeesdepends on magnitude of impulse

fragmentation height = 587 km


1976-126A

+mostly

retrograde im

pulse

Nearly same apogee height; therefore,fragmentation occurred near apogee

Another example of satellite fragmentation in elliptical orbit

fragmentationheight = 2088 km


1977-065B

+

fragmentationheight = 1450 km

Fragmentationat a height otherthan apogee orperigee will exhibit somecombination ofthe previouscharacteristics


1975-004B

+

nearly circular;breakup at 750 km

A pure radial impulse altersboth apogee and perigee whilemaintaining the same orbitalperiod.

A particular explosive eventwill produce points above and below the “arms” of theGabbard diagram.

Since they appear to surround the parent satellite, theyare sometimes called “halo”debris


1961-015C

For low-altitudebreakups, the left arm of the Gabbarddiagram can collapsedue to orbital decay


441 pages

Summarizing, some of thequestions you can try to answer

using Gabbard Diagrams include:

• Initial orbit type

• Breakup location wrt apogee/ perigee

• Distinct asymmetries in breakup

Weighted Gabbard Diagrams include a 1,2,3,4,5 designation for each object, depending on radar cross-section (and therefore presumably mass)

By comparing the distributions of fragments of various mass, it is usually possible to distinguish between collision- or explosion-induced fragmentations


http://setas-www.larc.nasa.gov/index.html

http://setas-www.larc.nasa.gov/LDEF/

NASA Web ResourcesIn-Situ Measurements


NASA's Long Duration Exposure Facility (LDEF) was designed to provide long-term

data on the space environment and its effects on space systems and operations.

• LDEF had a nearly cylindrical structure

• 57 experiments were mounted in 86 trays about its

periphery and on the two ends.

• The spacecraft measured 30 feet by 14 feet and

weighed ~21,500 pounds with mounted experiments

• LDEF remains one of the largest Shuttle-deployed payloads

• LDEF was deployed in orbit on April 7, 1984 by the

Shuttle Challenger.

• LDEF was retrieved on January 11, 1990 by the

Shuttle Columbia.



Largest impact - side view

Crater & Ejecta

Thermal Blanket Penetration

On-Orbit Thermal Blanket

ASEN 5335 - Aerospace Environment -- Orbital Debris 65Blanket penetration

Typical Aluminum Impact Typical Aluminum penetration

Metal Silica Oxide (MOS) detector

Beta clothpenetration


Trapped Van Allen protons (E ~100 - 1000 Mev) in theSouth Atlantic Anomaly (SAA) account for most of theenergetic particle exposure on LDEF


The LDEF observations revealed data on crater numbers (and fluxes) as a function of crater size, surface orientations relative to the spacecraft orbiting velocity vector, and surface materials, including metals, polymers, composites, ceramics and glasses, some with coatings and paints applied.


Some effects originated from preflight & postflight exposures, and Shuttle sources, as well as on-orbit material degradation.

Some thin polymeric films and blanket materials were virtually destroyed and created on-orbit debris that were distributed over adjacent surfaces.

A low-density particulate debris cloud in LDEF's wake was observedas the Shuttle approached for retrieval.

Inorganic thermal-control paints, anodized aluminum and silverized Teflon thermal-control blankets maintained their optical properties, and thus, their thermal control function.

Organic materials such as Mylar, Kapton, paint binders, and bare composites showed the expected severe erosion and degradation under atomic oxygen exposure. Coated composite materials survived and generally maintained their mechanical properties.


Typical List of LDEF Experiments (Systems)


Typical List of LDEF Accomplishments (Materials)

Besides LDEF,A number ofother missionsprovide datato the SpaceEnvironmentsand TechnologyArchive


The New NASA Orbital Debris Engineering Model ORDEM2000

• LEO - 200 - 2000 km• Current version - windows 95/98/2000/NT computers & Unix• http://www.orbitaldebris.jsc.nasa.gov/• Supercedes ORDEM96• Based on “finite element” concept, rather than curve-fitting• Two modes: 1. Orbiting spacecraft 2. Ground-based detection

Provides Users1. Debris flux onto spacecraft designers

Spacecraft surfaces and operators

2. Debris detection rate Debris observers

• Provides statistical debris environment as a function of altitude, inclination, & size distributions -- EVOLVE inputs used to extrapolate to 2003

• Similar ESA model -- MASTER’99• For satellite breakup risk assessment --- use NASA SBRAM• For more realistic long-term debris evolution --- use NASA EVOLVE


Data Sources

• Primary:SSN catalog to build the 1-m and 10-cm populations

Haystack radar data to build the 1-cm population

LDEF msmsts. to build the 10-m and 100-m populations

Other sources used to verify and validate model predictions

•

•

•


Used theoretical & experimentalequations and empirical fitting to relate crater depth and material density to particle density and impact speed.

Extrapolated to non-LDEF altitudes


Analysis of some LDEF surfaces allowed estimates of the relative fluxes of artificial debris and

micrometeoroids

Fitted meteoroid crater distribution

Craters due to meteoroids + unknowns

Craters due to debris

Cu

mu

lati

ve

nu

mb

er

Fitted crater debris distribution

Crater size (microns)

CME gold surface


EVOLVE was used to extrapolate the current orbital debris environment into the future

Nu

mb

er/k

m2


Sample ORDEM2000 Output:Debris Flux on ISS in 2005

No

/m2/

year

Diameter (cm)


ORDEM2000 Comparisons with Observations





Cu

mu

lati

ve N

um

ber

ORDEM 2000

STS


Mitigation is the Best Strategy for Diminishing Future Orbital Debris Impacts

Debris mitigation techniques span all phases of a space system’s life

Launch/Deployment

MissionTermination

Operations

Protect Assets by ….• shielding• active/passive avoidance• redundancy• avoid trackable objects

Mitigation of• spent rocket stages• separation devices• deployment mechanisms

Mitigation of ….• operational debris• explosions/collisions• secondary debris• deterioration

Removal by ….• disposal orbit• deorbit

• by design• active deboost

Documents

ASEN 5335 - Aerospace Environment -- Orbital Debris 1 Coronal holes and Solar wind speed and density The interplay between the inward pointing gravity