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Электронная библиотека астронома-любителя. Книги по астрономии, телескопостроению, оптике.
Дата: 28 апреля 1998 (1998-04-28)
От: Alexander Bondugin
Тема: Cassini Update - April 26, 1998
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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
CASSINI MISSION STATUS
April 26, 1998
The Saturn-bound Cassini spacecraft successfully performed a
flyby of the planet Venus this morning, coming about 284
kilometers (176 miles) from the Venusian surface. The flyby gave
the Cassini spacecraft a boost in speed of about 7 kilometers
per second (about 4 miles per second) help the spacecraft reach
Saturn in July 2004.
"All indications are that the spacecraft did exactly what we
expected," said Deputy Program Manager Ronald Draper at NASA's
Jet Propulsion Laboratory, Pasadena, CA. "Everything seems to be
right on the mark." Cassini was launched from Cape Canaveral,
FL, on October 15, 1997. Cassini was built by and its mission is
managed by JPL. It is an international mission involving NASA,
the European Space Agency and the Italian Space Agency.
NASA's Deep Space Network telecommunications antennas in
California's Mojave Desert and near Madrid, Spain, tracked the
spacecraft as it made its closest approach to Venus at 6:52 a.m.,
Pacific Daylight Time (Earth-received time). One-way light time
to the spacecraft from Earth was about 7-1/2 minutes.
Leaving Venus, the spacecraft was moving at more than
141,000 kilometers per hour (87,000 miles per hour). Science
instruments on the spacecraft searched for lightning in Venus's
atmosphere during the flyby, and the radar instrument onboard was
activated to test a bounced signal off Venus's surface.
Today, Cassini is about 136 million kilometers (about 85
million miles) from Earth.
In its long trajectory to Saturn, Cassini will perform
another flyby of Venus next June, one of Earth in August 1999,
and one of Jupiter in 2000. All of the flybys impart more speed
to the spacecraft to allow it to reach its final destination of
the Saturnian system. After it enters orbit around Saturn in
2004, Cassini will study the ringed planet, its moons and ring
system for at least four years. It will also deliver a
scientific probe called Huygens to parachute to the surface of
Saturn's largest moon, Titan.
#####
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Дата: 28 апреля 1998 (1998-04-28)
От: Alexander Bondugin
Тема: * SpaceNews 20-Apr-98 *
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SB NEWS @ AMSAT $SPC0420
* SpaceNews 20-Apr-98 *
BID: $SPC0420
=========
SpaceNews
=========
MONDAY APRIL 20, 1998
SpaceNews originates at KD2BD in Wall Township, New Jersey, USA. It
is published every week and is made available for non-commercial use.
* FUJI-OSCAR-29 NEWS *
The FO-29 satellite was switched into Mode JA on 1998-Apr-20 at 0700 UTC
because the command staion detectd 2 bit errors in the on-board-computer.
Resetting and reloading software into OBC will take a while, and the
satellite will remain in Mode JA until that time.
[Info via Kazu Sakamoto, JJ1WTK]
* OSCAR-11 NEWS *
In response to many requests for information regarding methods of decoding
OSCAR-11 signals, Clive Wallis has added a package of information to his
OSCAR-11 Web site regarding this topic. The web site also contains some
software for capturing data and decoding ASCII telemetry and WOD. There
is an archive of raw data (mainly WOD) for analysis, which is continually
being expanded as new data is captured.
The web site also contains some audio files, including a recording of the
Mode-S beacon which plays for 20 seconds. The other audio files are
examples of each type of data transmitted by OSCAR-11, and each one plays
for about ten seconds. All the audio files are zipped so that they can
be played off-line. They should help listeners identify the various
types of data, and give an indication of the signal quality required
for successful decoding.
The URL of Clive's OSCAR-11 Web page is:
http://www.users.zetnet.co.uk/clivew/
When the previous OSCAR-11 report was written, ground control operations
were taking place to investigate a "shut down" that had occurred a few
days previously. These operations were successful and normal service
has been restored. During the period 1998-Mar-21 to 1998-Apr-15,
excellent signals have once again been received from the 145.826 MHz
beacon.
Reception reports of the Mode-S beacon have been received from Mike,
WL7BQQM, Ed K9EK, and Jim KK3K. These reports were all received after
the "shut down" occurred, indicating that beacon is still OK. Many
thanks for those reports.
Since the "shut down", the telemetry indicates that there is a reduction
in the 14 volt line current of about 50 mA and a reduction in the +5 volt
current of about 25 mA. The reason for these changes is not obvious as
the status telemetry does not show that any units have been switched off.
The only obvious change in status telemetry is that the four bits associated
with the CCD camera integration period and gain have changed from ones to
zeros. The camera power is OFF (unchanged).
For several years, Clive has been monitoring the efficiency of the power
conversion process on OSCAR-11 (the ratio of power output to power input).
Power input = Sum of solar array currents * Array voltage
Power output = Battery volts * (Charge current + 14volt line current)
The efficiency calculated in this way has usually been around 80 to 85%.
However since the "shut down" it has fallen to around 65 to 70%. Clive
welcomes explanations or suggestions regarding this anomaly.
A new WOD survey of channels 1, 2, 3, 61 (magnetometers) dated 1998-Mar-19
has been started. Anyone using this survey should note the unusual starting
time of 16:00:05 UTC.
The operating schedule is unchanged.
ASCII status (210 seconds)
ASCII bulletin (60 seconds)
BINARY SEU (30 seconds)
ASCII TLM (90 seconds)
ASCII WOD (120 seconds)
ASCII bulletin (60 seconds)
BINARY ENG (30 seconds)
There are also additional status blocks after each bulletin is transmitted,
and between ASCII TLM and WOD.
The Mode-S beacon is on, transmitting an unmodulated carrier, but telemetry
indicates that it has partially failed, and delivering only half power.
This beacon is a useful test source for those testing Mode-S converters
in preparation for the launch of P3-D. It is considerably weaker than
DOVE, which should be used for initial testing. Any reports of S-Band
beacon reception should be directed to Clive Wallis at: g3cwv@amsat.org.
The 435.025 MHz beacon is normally off. However, it can sometimes be
heard when the satellite is being commanded by ground control, ie.
within range of Guildford, UK. When the 435 MHz beacon is transmitting,
the 145 MHz beacon is normally off. The data transmitted is mainly
binary.
[Info via Clive Wallis, G3CWV]
* MIR SCHOOL DAY PLANNED *
Dr. Dave Larsen, N6CO, of the MIREX team has announced a special MIR School
Day communications test on 1998-Apr-27 between 1000 UTC and 2300 UTC. The
purpose of the test is to let as many schools as possible communicate
their position and brief message via MIR. To date, there are about 30
schools signed up, with only seven being outside of the USA.
As was demonstrated during the 1998-Mar-11 test, as many as 50 schools in
a single footprint can probably participate and still have an excellent
chance of being seen. If you can set up your TNC, and modest 2m FM
transceiver to an omni antenna at a school, then you are welcome to
participate. For details, see the previous announcements on the subject,
or browse http://web.usna.navy.mil/~bruninga/mirex.html.
[Info via Bob, WB4APR]
* GPS THREAT TO 1.2 GHz BAND *
The ARRL Letter, dated 1998-Apr-04 stated that the second civilian
frequency for the Global Positioning System (GPS) could wind up within
Amateur Radio's secondary allocation at 1.2 GHz. A decision on whether
the new, second frequency will be 1205 or 1250 MHz is expected to be made
in August. An allocation at 1250 MHz could mean the end of Amateur Radio
in the band between 1240 and 1260 MHz. The Amateur 23-cm band runs from
1240 to 1300 MHz.
In February 1997, the Departments of Transportation (DOT) and Defense (DOD)
announced an agreement assuring civilian GPS users of a second frequency,
referred to as L5, and considered essential for critical civilian GPS uses.
According to a DOD news release, the White House Commission on Aviation
Safety and Security, chaired by Vice President Al Gore, "called for the
establishment of a second civil frequency as part of a broader program
to maintain US leadership in aviation and satellite technology."
Further information on this subject is available at:
http://www.defenselink.mil/news/Feb1997/b022797_bt095-97.html
[Info via John Santillo]
* FEEDBACK/INPUT WELCOMED *
Comments and input for SpaceNews should be directed to the editor (John,
KD2BD) via any of the paths listed below:
WWW : http://www.njin.net/~magliaco/
PACKET : KD2BD @ KS4HR.NJ.USA.NA
INTERNET : kd2bd@amsat.org, magliaco@email.njin.net
SATELLITE : AMSAT-OSCAR-16, LUSAT-OSCAR-19, KITSAT-OSCAR-25
<<=- SpaceNews: The first amateur newsletter read in space! -=>>
<<=- Serving the planet for 10 years -=>>
/EX
-=-=-=-=-=-=-=-=-=-=-=-=- John A. Magliacane, KD2BD -=-=-=-=-=-=-=-=-=-=-=-=-
Internet : kd2bd@amsat.org | Voice : +1.732.224.2948
Satellite : AO-16, LO-19, KO-25 | Morse : -.- -.. ..--- -... -..
Packet : KD2BD @ KS4HR.NJ.USA.NA | WWW : http://www.njin.net/~magliaco/
Video : 426.250 MHz/439.250 MHz | FAX : +1.732.224.2060
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