ASSESSING THE IMPACT RISK OF ORBITAL DEBRIS ON
and C. PARDINI
Spaceﬂight Dynamics Section, Consiglio Nazionale delle Ricerche (CNR), CNUCE Institute,
Via Alﬁeri 1, I-56010 Ghezzano – Pisa, Italy
(Received 15 June 1999; Accepted 3 December 1999)
Abstract. Tethers are being proposed for a growing number of space applications. However, they may be
particularly vulnerable to orbital debris and meteoroid impacts. In order to provide useful reference data for
tether systems design, detailed analytical and numerical computations were carried out to assess the average
impact rate of artiﬁcial debris and meteoroids. The speciﬁc geometric properties of tethers as debris targets,
when compared to typical satellites, are discussed, and the results obtained are presented in tabular form, as
a function of debris size and tether diameter.
The computations were carried out for six circular orbits, spanning three altitudes (600, 800 and 1000 km)
and two inclinations (30
). Tether diameters in between 1 mm and 2 cm and debris larger than 0.1 mm
were considered in the analysis. The collision risk of tethers with spacecraft and upper stages in orbit was
estimated as well.
In the debris interval and orbital regimes considered, artiﬁcial debris represent the dominant contributor
to the impact rate. At 600 km and in the 0.1–10 mm size range, the meteoroid and orbital debris impact rates
are still comparable; however, at higher altitudes and in the 1–10 cm size range, meteoroids contribute 20–30
times less to the collision probability.
The results obtained conﬁrm that for single-strand tethers in low Earth orbit the probability to be severed
by orbital debris and meteoroid impacts is quite signiﬁcant, making necessary the adoption of innovative
designs for long duration missions.
Keywords: debris mitigation, impact rate computations, meteoroids, orbital debris, spaceborne tethers
Abbreviations: ASI – Agenzia Spaziale Italiana (Italian Space Agency); CODRM-97R –
1997.0 CNUCE Orbital Debris Reference Model (Revised); CNUCE – former Centro
Nazionale Universitario di Calcolo Elettronico; NASA – National Aeronautics and Space
Administration; ORDEM96 – Orbital Debris Engineering Model 1996 (NASA); SDIRAT –
Space Debris Impact Risk Analysis Tool; TiPS – Tether Physics and Survivability Experi-
ment; TSS – Tethered Satellite System.
After many studies and proposals, back in the 70s and in the 80s, several space tether
related activities have been carried out in the 90s (Cosmo and Lorenzini, 1997). Even though
spaceborne tethers encountered a certain number of problems and setbacks, good ﬂight data
are now available to a growing scientiﬁc community, making possible the introduction of
Author for correspondence (E-mail: Luciano.Anselmo@cnuce.cnr.it).
Space Debris 1, 87–98, 2000.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.