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EXTREME ULTRAVIOLET EXPLORER PRESS KIT
JUNE 1992
Release: 92-64
EUVE SATELLITE TO EXPLORE NEWLY OPENED WINDOW
The extreme ultraviolet is one of the least-studied portions of the
electromagnetic spectrum. Now, with the launch of NASA's Extreme
Ultraviolet Explorer (EUVE) satellite, this new window on the universe
will be opened to detailed study.
EUVE, NASA's 67th Explorer mission, will be the first satellite to
make both spectroscopic and wide-band observations over the entire
extreme ultraviolet (EUV) region. It is scheduled for launch aboard a
McDonnell Douglas Delta II expendable launch vehicle from Cape Canaveral
Air Force Station, Fla., on June 4, 1992. EUVE is designed to operate
for at least 18 months from a 340-mile Earth orbit and will orbit the
Earth every 96 minutes.
This unique satellite consists of four telescopes -- the most
powerful set of EUV telescopes ever flown. Three instruments will map
the entire sky to determine the existence, direction, brightness and
temperature of sources of extreme ultraviolet radiation. The fourth
instrument is designed to make spectroscopic observations to determine
the composition and temperature of the EUV sources discovered during the
sky mapping. Some of the objects EUVE is likely to detect and study are
white dwarf stars, binary star systems and the hot outer atmospheres
(coronae) of stars similar to the sun.
From the many objects of astronomical interest discovered during the
EUVE all-sky survey and other objects already thought to be observable in
the extreme ultraviolet, guest observers will propose to study targets
using the spacecraft's fourth instrument, the extreme ultraviolet
spectrometer.
The EUVE is one of a long line of relatively low-cost, small-to-
moderately sized missions that make up the Explorer program. Since the
Explorer Program began in 1958, these missions have given scientists
worldwide a new understanding of astronomy and astrophysics, providing
them an opportunity to probe nearly every region of the electromagnetic
spectrum from infrared radiation to gamma rays.
Goddard Space Flight Center, Greenbelt, Md., is responsible for the
design, construction, integration, checkout and operation of EUVE. The
spacecraft's science instrumentation was designed, constructed and
calibrated by the Space Science Laboratories of the University of
California, Berkeley. The EUVE is managed by Goddard for NASA's Office of
Space Science and Applications.
SCIENCE OBJECTIVES
Astronomers use the term "extreme ultraviolet" (EUV) to refer to the
high-energy end of the ultraviolet portion of the electromagnetic
spectrum. Like other forms of light such as infrared and X-rays, EUV
light is blocked by the Earth's atmosphere. It must be studied from
space. In fact, even the very low density gas found between the stars
can block EUV light. Initially, astronomers thought it would be
impossible to detect EUV rays from sources beyond our solar system.
However, the sun now is known to lie within an unusually hot
transparent region of interstellar space. This region, about 250 light-
years in diameter, is often called the local bubble. Apart from a few
small wisps of cold, opaque gas, it is mostly transparent to EUV
radiation. EUV light from very distant stars beyond the local bubble is
unlikely to reach the Earth's vicinity and thus, EUVE will detect sources
mostly in Earth's stellar neighborhood.
The scientific mission of EUVE will initially consist of a 6-month
all- sky survey, together with a highly sensitive "deep" survey of a
limited portion of the sky. This will be followed by a spectroscopy
phase of at least 1 year. In the spectroscopy phase, individual targets,
whether discovered in the all-sky survey or identified from other
information, will be analyzed in detail through selected observations
made with an on-board extreme ultraviolet spectrometer.
The EUVE surveys will be conducted by astronomers from the Center
for Extreme Ultraviolet Astrophysics (CEA) at the University of
California, Berkeley, while the spectroscopic studies will be performed
by guest observers, selected through peer review.
As in the case of earlier Explorer missions, the most exciting
discoveries may be those that are unexpected. Objects thought to be well
understood may display surprising properties at extreme ultraviolet
wavelengths, and it is even conceivable that entirely new classes of
celestial objects may be discovered.
RESPONSIBILITIES
Observatory Goddard Space Flight Center
Telescopes Center for EUV Astrophysics,
University of California, Berkeley
Explorer Platform Spacecraft Fairchild Space,
Germantown, Md.
Delta II Launch Vehicle McDonnell Douglas, U.S. Air Force
and NASA
MISSION TIMELINE
Event
Time Altitude Velocity
(Min:Sec) (St. Miles) (MPH)
Liftoff 0:0 0 0
Six solid rocket
motors jettison 1:02 8.75 1,929
14.08 km 3,104.3 kmh
Three solid rocket 2:02 27.14 4,492
motors jettis 43.6 km 7,228.9 kmh
Main engine cutoff 4:24.5 64.05 12,682
103.07 km 20,409.1 kmh
Second stage 4:38 69.3 12,680
ignition 111.5 km 20,405.9 kmh
Fairing release 5:05 78.5 12,855
126.3 km 20,687.5 kmh
Second stage 11:11.9 110.17 17,699.9
engine cutoff 177.3 km 28,484.5 kmh
Second stage 66:53 328.83 16,791.7
restart 529.2 km 27,022.8 kmh
Second stage 67:12 328.22 16,994.4
engine cutoff (2) 528.2 km 27,349.08 kmh
Spacecraft 71:05 327.99 16,995.3
separation 527.83 km 27,350.53 kmh
THE INSTRUMENTS
EUVE contains four telescopes, each 15.7 inches across. The three
scanner telescopes and the deep survey/spectrometer telescope represent
the state-of-the-art in extreme ultraviolet technology. These
instruments, developed by scientists and engineers at the University of
California, Berkeley, are mounted in the payload module, which is
installed as a unit on the Explorer Platform spacecraft. The spacecraft
was designed and built by Fairchild Space in Germantown, Md., under
Goddard management.
Each of the EUVE scanner telescopes is about as large as a
55-gallon oil drum and weighs about 260 pounds. The deep survey
telescope/spectrometer weighs about 710 pounds.
Two of the scanning telescopes are nearly identical to verify
observations and to ensure a backup capability in the event of a
malfunction. They are used for observing at the high-energy end of the
extreme ultraviolet spectral band (70-400 Angstroms) -- the energy range
within which most sources are expected to be detected. These telescopes
have gold-plated mirrors, with very small grazing angles to reflect the
maximum amount of radiation at these higher energies.
The third scanner is specially designed to observe at the
low-energy end of the extreme ultraviolet spectral band (400-760
Angstroms). Its mirrors are plated with a special nickel alloy and use
larger grazing angles to reflect the maximum amount of lower energy
radiation.
The Deep Survey/Spectrometer telescope's opening, or aperture, is
divided into six equal segments. Radiation from three of these segments
is focused by the grazing-incidence mirror onto the single deep-survey
detector. During the survey phase, this telescope will make
long-exposure observations while being pointed down the dark shadow cast
by the Earth, allowing it to detect much fainter sources than the
all-sky survey scanners.
Radiation from the other three mirror segments is intercepted by
diffraction gratings that spread the radiation into beams of different
energy. The beams then are directed to the spectrometer's three
detectors. During spectroscopy studies, the spectrometer will analyze
the wavelength distribution of radiation from individual sources to
determine their temperature and chemical composition.
SPACECRAFT OPERATIONS
The Explorer platform spacecraft, plus the science payload,
comprise the Extreme Ultraviolet Explorer observatory. The observatory
is thermally controlled to protect the science payload from extreme
temperature changes. This protection is especially important because
orbital night and day occur about 16 times each Earth day as the
satellite circles the planet.
Like most satellites, the Extreme Ultraviolet Explorer is solar
powered. Photovoltaic cells on the satellite's solar array panels
convert solar energy into electricity, which is stored in rechargeable
batteries. At the beginning of the mission, the arrays will provide the
spacecraft with more than 1,000 watts of power during its journey around
Earth. Three hundred watts will be allotted to power the science payload
-- one-fourth the power needed to operate a typical microwave oven.
MISSION OPERATIONS
During the mission, Goddard's Payload Operations Control Center
(POCC) will be responsible for communications with the observatory,
transmitting commands and receiving science and engineering data. The
center then will route all science-related information to the University
of California, Berkeley.
NASA's Tracking and Data Relay Satellite System (TDRSS) plays an
integral role in mission communications. The observatory first
transmits data to a relay satellite, located 22,300 miles above the
Earth in geostationary orbit, which sends the information to the TDRSS
ground station at White Sands, N.M. From there, the data are relayed up
to a commercial communications satellite, also in geostationary orbit,
and down to Goddard. Finally, the scientific data are sent over
telephone lines to Berkeley.
SCIENCE OPERATIONS
While the Goddard Space Flight Center controls mission operations,
the Center for Extreme Ultraviolet Astrophysics (CEA) will coordinate
science operations, monitor instrument performance and collect data.
CEA, which operates from a dedicated building near the Berkeley
campus, includes a Science Operations Center and a Science Data Analysis
Facility. The Science Operations Center will work closely with Goddard
mission planners to coordinate the acquisition of scientific
measurements and command the instruments. The satellite's raw science
telemetry and processed data will be archived at the Science Data
Analysis Facility. There, Berkeley scientists will produce the all-sky
survey catalog and sky map and study data from the mission's deep
survey.
In addition, Berkeley will support the NASA-sponsored Guest
Observer Program during the mission's spectroscopy phase. One of
Berkeley's tasks will be scheduling spectroscopic observations for the
guest observers, who can interpret data either at their home
institutions or at the Berkeley facility.
PAYLOAD PROCESSING
The Extreme Ultraviolet Explorer flight elements arrived at Hangar
AE on Cape Canaveral Air Force Station (CCAFS) at the end of January.
The Payload Module was flown into the CCAFS Skid Strip by an Air Force
C-5 aircraft on Jan. 27, 1992 and the Explorer Platform was delivered by
truck on Jan. 28. Processing was accomplished in Hangar AE, a NASA
facility on CCAFS by the Goddard Space Flight Center's EUVE
NASA/contractor team with support from the Kennedy Space Center's
Payload Operations Directorate. After initial checkout, the Explorer
Platform was mated with the science payload module on Feb. 24.
A milestone was reached on March 6 when the first "countdown plus
early orbit" mission simulation was successfully completed. This
exercise began at a simulated launch minus 18-hours and continued
through launch plus 48 hours. A second simulation was successfully
completed on April 21.
After achieving a simulated orbit, the EUVE Payload Operations
Control Center (POCC) at Goddard and the EUVE Science Operations Center
(ESOC), located at the University of California, Berkeley, sent
simulated commands to the spacecraft. The spacecraft was to be moved to
the launch pad in mid- May for mating and integration with the Delta II
launch vehicle.
LAUNCH OPERATIONS
The U. S. Air Force's 1st Space Launch Squadron, 45th Operations
Group, 45th Space Wing, is responsible for preparation and launch of the
Delta II which will carry the Extreme Ultraviolet Explorer into orbit.
The Delta II underwent buildup on Pad A of Launch Complex 17 at
CCAFS in mid-April. This activity includes erecting the first stage and
interstage, mating the nine solid rocket boosters in place around its
base, and then hoisting the second stage atop the first stage. The
significant mechanical and electrical tests are scheduled to run between
May 10 and May 20.
On approximately May 15, the EUVE spacecraft is scheduled to arrive
at the pad to be mated to the Delta second stage. EUVE's integrated
checks atop the vehicle and final spacecraft functional tests were
planned to run between May 20 and May 24. During this period, workers
will install the nose fairing around the spacecraft.
The hypergolic propellants will be loaded aboard the Delta second
stage approximately 2 days prior to launch. The RP-1 fuel (kerosene
propellant) and the super cold, liquid oxygen used as an oxidizer by the
first stage both will be loaded aboard during the terminal countdown.
Launch operations will be conducted from the Complex 17 blockhouse
by a joint USAF/McDonnell Douglas team under the direction of the 45th
Operations Group.
As this mission involves launch of a NASA payload, the agency has
responsibility for supporting EUVE flight preparations. A NASA KSC
launch manager will represent all agency interests during vehicle
preparations and the launch countdown and serve as NASA liaison with the
Air Force. The launch manager will be located in the Mission Director's
Center at CCAFS to monitor launch countdown operations and to provide
the final NASA concurrence for launch to the USAF launch director.
LAUNCH VEHICLE
A U. S. Air Force Delta II 6920-10 expendable launch vehicle will
lift the EUVE into low-Earth orbit for NASA. Built by McDonnell Douglas
Space Systems Company (MDSSC) of Huntington Beach, Calif., the Delta II
has a perfect launch record.
The EUVE flight will be the second time a 10-foot diameter fairing
has been used on a Delta vehicle. Its first use was in 1990 for launch
of the Roentgen Satellite (ROSAT) mission. The fairing, built in three
sections, is based on the Titan family of fairings MCSSC has built for
years.
NASA funded development of the 10-foot fairing to accommodate the
ROSAT, EUVE and other payloads requiring a larger volume than offered by
the 9.5-foot and 8-foot fairings regularly flown on Delta.
The EUVE launch is scheduled to be the 24th flight for the Delta
II. Delta's origins reach back to the mid-1950s when the U. S. Air Force
developed the Thor intermediate-range ballistic missile. NASA later
modified the Thor, a single-stage, liquid-fueled missile for the Delta
launch vehicle.
The two-stage Delta II carrying EUVE consists of four major
assemblies, the first stage, including nine strap-on solid rocket
motors, the interstage, the second stage and the payload fairing.
The Delta II is 123.4 feet tall and 8 feet in diameter. The
payload fairing is 26 feet tall and 10 feet in diameter. The first
stage main engine has a liftoff thrust of 207,000 pounds and each of the
nine solid strap-on motors has a sea-level thrust of 97,070 pounds. The
main engine and six of the nine solid motors are burning at liftoff,
providing a total thrust of 789,420 pounds.
The second set of three solid strap-on motors is ignited during the
first stage burn. The second stage engine has a vacuum-rated thrust
level of 9,645 pounds.
Several major subcontractors to MDSSC contributed to the Delta
vehicle. The Rocketdyne Division of Rockwell, Canoga Park, Calif., is
responsible for the first stage engine. Aerojet TechSystems Co. of
Sacramento, Calif., builds the second stage engine. Morton Thiokol of
Huntsville, Ala., manufactures the solid rocket boosters and Delta
Systems of Goleta, Calif., produces the guidance computer.
MISSION MANAGEMENT
NASA Headquarters:
Dr. Lennard A. Fisk, Associate Administrator, Office of Space Science
and Applications
Dr. Charles J. Pellerin, Jr., Director, Astrophysics Division
John Lintott, Program Manager
Dr. Robert Stachnik, Program Scientist
Charles Gunn, Director, Expendable Launch Vehicle and Upper Stages
Goddard Space Flight Center:
Dr. John Klineberg, Center Director
James Barrowman, Project Manager, Explorers and Attached Payloads
Frank Volpe, Associate Project Manager for EUVE
Dr. Yoji Kondo, Project Scientist
Pete O'Neill, Project Manager, Satellite Servicing Project
Llewellyn Nicholson, EUVE Flight Operations Director
Robert Spiess, EUVE Spacecraft Manager
John Beckham, Delta Project Manager
University of California, Berkeley:
Prof. Stuart Bowyer, EUVE Science Principal Investigator
Dr. Roger Malina, Instrument Principal Investigator
Dr. Carol Christian, EUVE Guest Observer Project Scientist
Kennedy Space Center:
Robert L. Crippen, Center Director
John T. Conway, Director of Payload Management and Operations
J. L. Womack, Director, Expendable Vehicles, NASA Launch Manager
JoAnn H. Morgan, Director, Payload Projects Management
Thomas Rucci, EUVE Launch Site Support Manager
USAF 45th Space Wing, Patrick AFB:
Brig. Gen. Jimmy R. Morrell, Commander
Col. Michael R. Spence, Commander 45th Operations Group
Lt. Col. Randolph M. Moyer, Commander, 1st Space Launch Squadron,
Launch Director
McDonnell Douglas Space Systems Company:
Rich Murphy, Director, NASA/SDIO and Commercial Programs
Lyle Holloway, Director, Launch Sites
Jerry Winchell, Program Manager, NASA Programs
Jay Witzling, Deputy Director, NASA/SDIO and Commercial Programs
Jack Dodds, Launch Conductor