A publication of
The Orbital Debris Program Office
NASA Johnson Space Center
Houston, Texas 77058
April 2002
Volume 7, Issue 2.
NEWS
Release of ORDEM2000
J.-C. Liou
The new orbital debris engineering model
ORDEM2000 was released by the NASA Orbital Debris Program Office earlier this year.
The model is appropriate for engineering solutions requiring knowledge and estimate of the
orbital debris environment (spatial density, flux,
etc.) in the low Earth orbit region between 200
and 2000 km altitude. It can also be used as a
benchmark for ground-based debris measurements and observations.
The highlights of the new model include:
(1) a large set of observational data (both in-situ
and ground-based), covering the object size
range from 10 µm to 10 m, was incorporated
into the ORDEM2000 debris database, (2) a
new analytical technique was employed to convert observational data into debris population
probability distribution functions - these functions then form the basis of debris populations,
and (3) a finite element model was developed to
process the debris populations to form the debris environment. In addition, a more capable
input and output structure and a user-friendly
Graphical User Interface (GUI) are also implemented in the model.
ORDEM2000 has been subjected to a significant verification and validation effort. The
new model has been tested thoroughly and compared with all available data. Overall, it provides a very good description of the current debris environment. The model is now being used
for Space Shuttle and International Space Station for debris risk assessments. ORDEM2000
is available at the Orbital Debris Program Office website at http://sn-callisto.jsc.nasa.gov/
model/modeling.html.
v
The Leonid Storm of 2001
bling the collection
of data over the entire duration of the
storm. The disappointment
came
from the realizations that all of the
forecasts
were
wrong in some details (mine and Peter Brown’s apparently fared the
worst), and that a
fair amount of work
would be needed to
locate manpower
and funds to reduce
the 2+ terabytes of
4000
3500
3000
2500
ZHR
B. Cooke
On the night of November 17-18 of this
past year, the Leonid meteor shower reached
storm level activity over the United States for
the first time since 1966. To most, Mother Nature treated them to a spectacular sky show,
with meteors appearing every few seconds at
the first maximum near 10:30 UT (04:30 CST).
To those of us involved in the forecasting and
observing of the Leonids, the 2001 storm
proved to be a strange mix of excitement and
disappointment… It was exciting in that the
forecasts proved to be reasonably accurate in
terms of the level and duration of the activity
and that, of the 6 observation sites manned by
MSFC and University of Western Ontario personnel (Eglin AFB, Huntsville, Apache Point,
Haleakala, Guam, and Ulan Baator, Mongolia),
only Guam experienced cloudy weather, ena-
2000
1500
1000
500
0
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
November 18 (UT)
(Continued on page 2)
(Continued on page 2) Figure 1. 2001 Leonid ZHR profile (IMO, January 2002).
Inside...
Reentry Survivability Analysis of the Upper Atmosphere Research Satellite (UARS)...... 2
Albedo Distributions of Debris ............................................................................. 4
Meeting Reports ................................................................................................. 5
1
The Orbital Debris Quarterly News
NEWS
The Leonid Storm of 2001, Continued
(Continued from page 1)
10000
Lyytinen and Asher/McNaught ZHR profile constructed using expression given by Brown (1999)
Brown/Cooke
Asher/McNaught
9000
1866
Lyytinen
Jenniskens
Final IMO
8000
7000
Projected ZHR
video data collected by the observing teams.
As depicted in figure 1, the 2001 Leonids
had two major peaks; the first, mentioned above,
reached a maximum Zenith Hourly Rate (ZHR)
of around 1600 at 10:35 UT. According to the
International Meteor Organization, it is bimodal
in nature, with a secondary peak some 24 minutes later, at approximately the same level. The
second and larger peak occurred over Asia, at
approximately 18:15 UT. It reached a ZHR of
3400, close to the level of the 1999 storm, which
peaked at 3700 Leonids per hour. However,
unlike the brief outburst of 1999, the 2001
Leonids exhibited significantly elevated activity
(ZHRs > 300) for over 12 hours, resulting in a
much greater fluence; a current estimate would
place it at approximately 4.5 times that of 1999,
or about 7 Leonids km-2 down to mass of approximately 10 µg. This is in good agreement
with the forecast fluence levels of 5 to 10
Leonids km-2. It is somewhat ironic that satellite
operators devoted much more attention to the
1999 shower than the 2001 apparition, where
the risk was roughly 5 times greater.
While the forecasts did a good job of characterizing the length and overall characteristics
of the 2001 Leonids, they fail in the “fine” details. In particular, forecasting the level of the
maxima remains problematic, as a glance at figure 2 shows. The Brown/Cooke profile looks
particularly disconcordant; this is due to the dy-
6000
5000
1766
4000
1699
17th century material
3000
2000
1799
1000
0
5
6
7
8
9
10
11
12
13
14
15
16
Nov 18, 2001 (UT)
17
18
19
20
21
22
23
24
Bill Cooke/MSFC - 11/01/2001
Figure 2. 2001 Leonid forecasts.
namical model placing the 1799 stream closer to
Earth, resulting in the peak at 13:00 UT, resulting in a much greater contribution to the ZHR
profile. It is hoped that the forecasters will take
a good look at the 2001 data and use it to revise
their models, as storm level Leonid activity is
once again projected for 2002. At Marshall,
work is progressing in devising an automated
method of reducing the video data, the results of
which will be used in producing a revised 2002
Leonid forecast.
v
Project Reviews
Reentry Survivability Analysis of the Upper Atmosphere Research Satellite (UARS)
W. C. Rochelle and J. J. Marichalar
The National Aeronautics and Space Administration (NASA) Goddard Space Flight
Center (GSFC) Upper Atmosphere Research
Satellite (UARS), which was launched September 12, 1991 by the Space Shuttle STS-48, will
be decommissioned in 2002-2003. It is currently planed to allow the spacecraft to reenter
in an orbital decay mode. In accordance with
NASA Policy Directive 8710.3, GSFC performed a reentry analysis of the UARS spacecraft using the NASA Lyndon B. Johnson
Space Center (JSC) Debris Assessment Software (DAS). The GSFC DAS results showed
the UARS spacecraft to be non-compliant with
NASA Safety Standard 1740.14 Guideline 7-1,
which requires the surviving debris of an uncontrolled spacecraft reentry to produce a risk
to ground population no greater than 1:10,000.
In response to the results, GSFC requested an
analysis be performed using the higher-fidelity
Object Reentry Survival Analysis Tool
(ORSAT), developed by JSC and Lockheed
Martin Space Operations (LMSO).
The approximately 5670 kg UARS satellite
is providing data on chemistry, dynamics, and
energy balance above the Earth’s troposphere
and coupling between these processes and other
atmosphere regions. It also measures ozone and
chemical compounds that affect chemistry processes in the ozone layer. The UARS observatory consists of a standard Multi-mission Modular Spacecraft (MMS) coupled to an Instrument
Module that includes ten science instruments
and various mission-unique components. The
starboard view of the UARS space, with the
locations of some of the instruments, the MMS,
and other elements, is shown in Fig. 1.
2
The UARS will be decommissioned upon
completion of its current Science Traceability
Mission. There is not enough propellant on
board or the spacecraft to reenter in a targeted
(controlled) entry mode. Eventually the orbital
decay of the UARS sp acecraft will cause it to
reenter the Earth’s atmosphere, resulting in
break-up and demise of most of the spacecraft
components. However, due to the mass, size,
and material properties of some of the components, there is an increased possibility of those
components surviving the atmospheric reentry
and posing a safety risk to the ground population.
In the reentry analysis performed using
ORSAT, entry interface for the UARS spacecraft was assumed to be 122 km, with initial
break-up occurring at 78 km. This point is the
(Continued on page 3)