[Federal Register Volume 62, Number 46 (Monday, March 10, 1997)]
[Notices]
[Pages 10879-10880]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-5735]


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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

[Notice (97-026)]


National Environmental Policy Act; Cassini Mission

AGENCY: National Aeronautics and Space Administration (NASA).

ACTION: Notice of intent to prepare a supplemental environmental impact 
statement (SEIS) for implementation of the Cassini mission to Saturn 
and its moons.

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SUMMARY: Pursuant to the National Environmental Policy Act of 1969 
(NEPA), as amended (42 U.S.C. 4321 et seq.), the Council on 
Environmental Quality Regulations for Implementing the Procedural 
Provisions of NEPA (40 CFR Parts 1500-1508), and NASA's policy and 
procedures (14 CFR Part 1216 Subpart 1216.3), NASA intends to prepare a 
supplement to the Cassini mission Final Environmental Impact Statement 
(FEIS). The SEIS will focus on updated information pertinent to the 
consequence and risk analyses of potential accidents during the launch 
and cruise phases of the mission. Such accidents could result in a 
release of plutonium dioxide from the three Radioisotope Thermoelectric 
Generators (RTG's) and the potential 157 Radioisotope Heater Units 
(RHU's) onboard the Cassini spacecraft. The currently planned mission 
involves the launch of the Cassini spacecraft from Cape Canaveral Air 
Station (CCAS), Florida, during the primary launch opportunity in 
October 1997.

FOR FURTHER INFORMATION CONTACT: Mr. Mark R. Dahl, NASA Headquarters, 
Code SD, Washington, DC 20546-0001; 202-358-0306.

SUPPLEMENTARY INFORMATION: The planned Cassini mission is an 
international cooperative effort of NASA, the European Space Agency, 
and the Italian Space Agency, to explore the planet Saturn and its 
environment. Saturn is the second-largest and second-most massive 
planet in the solar system and has the largest, most visible dynamic 
ring structure of all the planets. The planned mission is an important 
part of NASA's program for exploration of the solar system, the goal of 
which is to understand the system's birth and evolution. The Cassini 
mission would involve a 4-year scientific exploration of Saturn, its 
atmosphere, moons, rings, and magnetosphere. The Cassini spacecraft 
consists of the Cassini Orbiter and the detachable Huygens Probe.
    For several months, prior to its arrival at Saturn in June 2004, 
the spacecraft would perform scientific observations of the planet. The 
planned arrival date at Saturn provides a unique opportunity to have a 
distant flyby of Saturn's outer satellite Phoebe. About 3 weeks before 
its first flyby of Titan, Saturn's largest moon, the Huygens Probe 
would be released for a 2.5 hour parachute descent into Titan's 
atmosphere. The probe would sample and determine the composition of 
Titan's atmosphere during its descent, and gather data on

[[Page 10880]]

the moon's landscape. The Cassini Orbiter would then continue its 
Saturn orbital tour, providing opportunities for ring imaging, 
magnetospheric coverage, and radio (Earth), solar, and stellar 
occultations of Saturn, Titan, and the ring system. A total of 35 close 
Titan flybys have also been planned for the 4-year tour, along with 4 
close flybys of selected icy satellites, and 29 more distant satellite 
encounters. The scientific information gathered by the Cassini mission 
could help provide clues to the evolution of the solar system and the 
origin of life on Earth.
    The Cassini spacecraft would carry three RTG's that use the heat of 
decay of plutonium dioxide to generate electric power for the 
spacecraft and its instruments. The spacecraft would also use up to 157 
RHU's, each containing a small amount of plutonium dioxide, to generate 
heat for controlling the thermal environment of the spacecraft and 
several of its instruments.
    The Cassini FEIS was made available to Federal, state, and local 
agencies, the public, and other interested parties on July 21, 1995. In 
addition to the No-Action alternative, the FEIS addressed in detail 
three alternatives for completing preparations for, and operating the 
Cassini mission to Saturn and its moons. On October 20, 1995, utilizing 
the analyses in the FEIS along with other important considerations such 
as programmatic, technical, economic, international relations, and 
other factors, the Record of Decision selecting the Proposed Action was 
rendered.
    The Proposed Action consists of completing preparations for and 
implementing the Cassini mission to Saturn and its moons, with a launch 
of the Cassini spacecraft onboard a Titan IV(SRMU)/Centaur. The launch 
would take place at CCAS during the primary launch opportunity in 
October 1997. A secondary launch opportunity occurs in December 1997, 
with a backup opportunity in March 1999, both using the Titan IV(SRMU)/
Centaur. The primary launch opportunity would employ a Venus-Venus-
Earth-Jupiter-Gravity-Assist trajectory to Saturn; the secondary and 
backup opportunities would both employ a Venus-Earth-Earth-Gravity-
Assist (VEEGA) trajectory. The Proposed Action would allow the Cassini 
spacecraft to gather the full science return desired to accomplish 
mission objectives.
    Along with the No-Action alternative (ceasing preparations and not 
implementing the Cassini mission), the FEIS evaluated in detail two 
other mission alternatives. The March 1999 alternative would have used 
two Shuttle flights with on-orbit integration of the spacecraft and 
upper stage, followed by injection of the spacecraft into a VEEGA 
trajectory to Saturn. Due to the long lead-time in developing and 
certifying the new upper stage that would be needed to implement it, 
this alternative is no longer considered reasonable. Also, this 
alternative would have returned less science than the primary launch 
opportunity of the Proposed Action. The other mission alternative 
considered in the FEIS was the 2001 alternative, which would use a 
Titan IV(SRMU)/Centaur to launch the spacecraft from CCAS in March 2001 
on a Venus-Venus-Venus-Gravity-Assist trajectory. A backup opportunity 
in May 2002 would use a VEEGA trajectory. The 2001 alternative would 
require completing development and testing of a new high-performance 
rhenium engine for the spacecraft, as well as adding about 20 percent 
more propellant to the spacecraft. Science returns from this 
alternative would meet the minimum acceptable level for the mission.
    The FEIS analyses demonstrated that completing preparations for and 
implementing a normal Cassini mission would not significantly impact 
the human environment. The principal concern associated with all 
mission alternatives (except No-Action) was with accidents during 
launch and operation of the mission that have the potential to result 
in a release of plutonium dioxide from the RTG's and/or RHU's onboard 
the spacecraft. In response, NASA and the U.S. Department of Energy 
(DOE), using the best information available at that time, developed an 
array of representative accident scenarios that could potentially 
result in a release of plutonium dioxide from the RTG's. NASA and DOE 
analyzed the representative accident scenarios with respect to the 
consequences and risks. The results of those analyses were presented in 
the Cassini FEIS.
    Updated results from the continuing tests and analysis have 
recently become available for NASA review. This updated data indicates 
that there is new information relevant to environmental concerns and 
bearing on the impacts of the Proposed Action. NASA has determined that 
the purposes of NEPA will be furthered by preparation and issuance of 
an SEIS.
    The SEIS will address NASA's consideration of the updated data 
resulting from the ongoing analysis. The SEIS will compare the updated 
data with those in the FEIS and will focus on the areas where the 
largest differences in risk are estimated. The SEIS will address the 
Proposed Action, the No Action alternative, and the 2001 mission 
alternative which is still available to NASA.
Benita A. Cooper,
Associate Administrator for Management Systems and Facilities.
[FR Doc. 97-5735 Filed 3-7-97; 8:45 am]
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