Two More Satellite Breakups Detected

[From July 2001 issue of ORBITAL DEBRIS QUARTERLY NEWS, NASA JSC]

By P. Anz-Meador

The third fragmentation event of the year 2001 occurred on or about 29
April with the fragmentation of the Russian Cosmos 1701 spacecraft. The
NASA Johnson Space Center’s Orbital Debris Program Office was notified
by the US Space Command’s (USSPACECOM) Space Defense Operations Center
(SPADOC) of the assessed fragmentation on 1 May 2001. Ten (10) large
debris were tracked by the USSPACECOM Space Surveillance Network (SSN)
as of that date; as of 30 May 2001, no debris objects had entered the
Space Control Center’s (SCC) catalogue. Cosmos 1701 (Satellite Number
16235, International Designator 1985-105A) was in an orbit of 85 km by
25,570 km with an inclination of 62.9 degrees at the time of the event.
While this event represents the 17th known breakup of a Cosmos 862-class
payload since the first event in 1977, this event is dissimilar to all
preceding events. Assessed cause of the Cosmos 1701 fragmentation was
aerodynamic loading due to the low perigee of the vehicle, rather than
the deliberate destruction of the vehicle by an on-board explosive system.

Cosmos 1701 was an Oko-class vehicle. These vehicles perform missile
launch early warning duties in orbits very similar to the Russian Molniya
communications payloads. The three-axis stabilized vehicle is cylindrical
in shape with two solar array panels and an erectable sun shade for
the primary on-board sensor system. Dimensions of the cylinder are
approximately 2 m in diameter and 1.7 m in length; dry mass is on the
order of 1250 kg.

An analysis of the event, conducted the day the Orbital Debris Program
Office was notified of the fragmentation, indicates that the long-term
environmental consequences are minimal, as the parent object was in a
catastrophic decay from the original Molniya-type orbit. This lessens
the spatial density in low Earth orbit because of the large eccentricity
and low perigee of the vehicle’s orbit.

The second breakup event of the quarter took place about 16 June and
involved a Russian Proton K Block DM ullage motor, International
Designator 1991-025G, Satellite Number 21226. The SSN detected as many
as 100 debris in orbits similar to that of the parent object, which was
300 km by 18,960 km with an inclination of 64.5 degrees.

This was the 24th event of this type identified since 1984 (see Orbital
Debris Quarterly News, January 2001, for the previous breakup). The
breakups of the ~ 55 kg objects are assessed to be related to the
presence of residual propellants. The problem was recognized in the
early 1990’s, and no Block DM ullage motor launched since 1996 is
known to have experienced a fragmentation, in part due to design and
operational changes.