Your Sky by John Walker
the interactive planetarium of the Web.
You can produce maps ...
for any time and date, viewpoint, and observing location.
If you enter the orbital elements of an asteroid or comet,
Your Sky will compute its current position and plot it on the map.
(this looks very useful)
the Lunar and Planetary Institute
has Lunar Atlases, Lunar and Planetary Information Bulletin (LPIB),
claims to have planetary image libraries and a planetary cartography collection,
but they don't seem to be online
part of the
Universities Space Research Association
"enter the date, the U.T. time, and your longitude and
latitude ... to get a star map ... you can control such things
as the minimum magnitude of stars to show ... meteor
showers". It returns the map in Postscript, but has a nice
link to Ghostscript viewers.
``The one, the only, photograph of Earth''
by Neil Fraser, March 2001
laughs at the over-use of one particular photo of Earth,
and helps you find to other NASA archive photos of Earth.
tells where stars are in full 3D.
3D map programs,
Pointers to the entire
Includes source code.
Lots of information on real stars used in science fiction.
Nice photos of the moon; a to-scale graphic showing the size
of the earth, the size of the moon, the distance between them,
and geosync orbit.
(Please email me if you find any other to-scale astronomical
graphics -- -- I can't recall seeing *any* others on the 'web,
and only 2 on paper).
[FIXME: make a modified version to show GPS orbit]
Views of the Solar System
appears to have a picture of all the planets to-scale
(but all the *distances* between them shrunk very small
to get them all to fit).
"RXTE Finds Cannibal Star That May Be A Missing Link!"
SAX J1808.4-3658, is located 12,000 light years away towards the constellation Sagittarius.
SAX J1808.4-3658 is not only an X-ray pulsar, it is the fastest-spinning pulsar of its type ever seen.
Its rotation rate is upwards of 400 times a second, giving it a spin period of 2.5 milliseconds
millisecond pulsar PSR J0437-4715, with a distance of about 450 light years,
is the closest object of its kind.
It is bound together with a low-mass companion, a white dwarf, in a close binary star system
with an orbital period of 5.5 days.
The pulsar itself is spinning with a period of 5.75 ms.
glitches, a term given to the sudden change in pulsar spin frequency
A pulsar named
PSR J0537-6910 appears to have the highest rate of glitches of any known pulsar,
according to a team led by Frank Marshall
These glitches occur seven times more frequently than in the Vela pulsar,
the former "glitcher king," ...
Pulsars spin with clock-like precision,
keeping time to within a millisecond over the course of a year
as the spin very gradually slows down.
During a glitch, the pulsar suddenly starts to spin a little faster.
Rarely do astronomers see more than one or two big glitches in a pulsar
over many years of observation.
Yet PSR J0537-6910 has had six big glitches in about two-and-a-half years.
Each glitch releases more energy than our Sun does in 3,000 years.
PSR J0537-6910 is already in the record books as the fastest young (5,000 years old) pulsar,
spinning once every 16 milliseconds,
PSR J0537-6910 is also an X-ray pulsar not visible in other wavelengths.
It is located in our neighboring Large Magellenic Cloud...
article by Dr Jamie Love 2001
very easy-to-understand article explaining how telescopes, binoculars, etc. work.
Dr. Love recommendes binoculars or ``spotting scopes'' (monoculars)
over telescopes for those learning astronomy.
the Bradford Robotic Telescope Observatory
You can add your request to the queue,
and when your request bubbles to the top, it will
photograph your desired section of the sky
and return the photograph.
Archives of lots of photos already taken.
Has links to other online telescopes:
Schoolkids Can Use Net To Scan Stars - Albuquerque Journal
New Mexico schoolchildren will be able to log onto the Internet to
control a large research telescope as a result of an agreement recently
signed between the New Mexico Institute of Mining and Technology and the
LodeStar astronomy project.
"I have been using a color quickcam for astro photography with
good success. I am interested in hearing from others who
are doing similar things.
imaging the moon and planets.
It is low cost and it works well." --
< walter at bytecraft.com >
"SAOimage displays astronomical images in the
X11 window environment."
provides a large selection of options for zooming, panning, scaling,
coloring, pixel readback, display blinking, and region specification.
User interactions are generally performed with the mouse, but keyboard
alternatives are often available."
All source is available at
the Cassini-Huygens Mission to Saturn and Titan
``In 2004, Cassini-Huygens is scheduled to reach Saturn and its moons.
There the spacecraft will orbit around the system for four years;
Huygens will enter the murky atmosphere of Titan, Saturn's biggest moon, and
eventually descend via parachute onto its mysterious surface.''
Space Telescope Science Institute (STScI)
has tons of images and information about the
Hubble Space Telescope (HST) &
Next Generation Space Telescope (NGST)
NASA press releases and other information are available
automatically by sending an Internet electronic mail message
to firstname.lastname@example.org. In the body of the message (not the
subject line) users should type the words "subscribe
press-release" (no quotes). The system will reply with a
confirmation via E-mail of each subscription. A second
automatic message will include additional information on the
projects to employ resources of the moon and asteroids near Earth
in the near term (PERMANENT).
Some pretty inspirational stuff here.
NOAA's National Environmental Satellite, Data and Information Service - NESDIS
Search & Rescue Satellite Aided Tracking (SARSAT) System
commonly called "weather satellites".
Has a gallery of historical satellite images,
"GOES Full Disk images are updated every three (3) hours."
which shows the entire planet.
Today's Space Weather
shows a graph of
"Solar X-ray Flux"
has an archive of
"Full disk Helium 10830 image of the sun"
"Full disk H-Alpha image of the sun"
"Full disk Magnetogram image of the sun"
[DAV: how are Magnetogram images made ?]
This plot shows the orbital height of the ISS ...
Clearly visible are the re-boosts which suddenly increase the height, and
the gradual decay in between... caused by atmospheric drag.
``Only a few satellites are visible with the naked eye
We developed J-Pass to help you view some of the most visible satellite passes.''
[FIXME: tell Marshall Brain about this ? See previous web link.]
"The primary power source for micro satellites
is solar panels illuminated by the sun.
The sun provides power at a density of 1.3 kW per square meter.
solar panels with efficiencies varying from
14% for Si cells to
18 % for GaAs cells.
One square meter of Si panels can deliver a maximum of 182W in space.
Allowing for degradation of the cells and area for interconnects,
this figure drops to 150W.
are the single most limiting item
on the lifetime of a LEO spacecraft. Both
in terms of mass and the number of charge/discharge cycles."
REMOTE SENSING USING THE
UNIVERSITY OF SURREY'S MICROSATELLITES
low-cost 50 kg microsatellites.
has designed, built and launched ten such spacecraft
"electronic cameras with 2-dimensional CCD arrays
are the most suitable imaging technology for microsatellites.
Because they capture whole images in a single snap-shot,
they preserve the scene geometry
and are therefore immune to
the residual attitude drift experienced on microsatellites.
Of course, CCD cameras also possess the features of
compactness, robustness, low power, and
mechanical simplicity of all solid-state imagers."
"The sequencing of operations for each modular camera
is implemented locally by a Motorola 68HC11 microcontroller."
"The two T805 Transputers used on SSTL's microsatellites
are 20 MHz, 32-bit devices with 4 MBytes of error-protected memory each,
making them amongst the most powerful computers flown in space.
As with all computer modules (not microcontrollers)
flown on SSTL's microsatellites,
the Transputers do not hold their flight code in ROM.
Only boot code is hard coded,
and all applications software is uploaded in orbit.
This has permitted the remote sensing experiments to evolve whilst in orbit,
with the image processing and
compression software being upgraded as required."
"A number of approaches are used to
improve the 'information per byte' of imagery on the downlink.
Autonomous image analysis and selection
to reject images failing to meet specified interest / usefulness criteria
(usually uniform images caused by very cloudy scenes).
Generation of image previews
to let ground control decide which images should be prioritised for,
or alternatively discarded from, the downlink queue.
high compression (16:1) used for these 'thumb-nail' images
A compression routine known as
Adaptive Moment-Preserving Block Truncation Coding 
is implemented on PoSAT-1,
achieving compression ratios of between 2.5:1 and 4:1.
Although the compression is relatively modest,
the AMPBTC routine preserves fine detail
far more faithfully than many other popular routines,
especially JPEG which introduces significant compression artefacts.
" M. Rabbani & P. Jones: Digital Image Compression Techniques; SPIE Optical Engineering Press 1991."
check out the STS-73 shuttle web page for the most recent
science experiments regarding protein crystal growth in
microgravity -- http://shuttle.nasa.gov/sts-73/
under "Payloads" and then "experiments in
I (David Cary) have been told that there are some especially stable
points for placing satellites in Earth's orbit,
called Lagrange points
You should be able to spot them in these graphs I've made.
(Darkest blue == smallest acceleration in a 1 orbit/month circular orbit).
There are many other other fairly stable orbits
(simple circular orbits; elliptical orbits)
other than the ones shown here.
Unfortunately, I have not yet been
able to find all 5 Lagrange points in my graphs.
According to the sources below, there
are 5 Lagrange points in a 2 body system.
L4 (ahead of the secondary)
L3 (O) L1 o L2
L5 (following the secondary)
(O) = primary body
o = secondary body
L4 and L5
are called Trojan points.
I have heard that L1, L2, L3 are points
of unstable equilibrium,
but L4 and L5 are points of stable equilibrium.
Why can't i see them on my graphs ?
"Quasi-satellites, a strange class of Solar System object, may exist in the outer reaches of our Solar System"
paper by Paul Wiegert and Kimmo Innanen and Seppo Mikkola
"Over 400 hundred asteroids remain stable either 60 degrees ahead of or behind Jupiter as it goes around its orbit;
both planet and asteroids take 11.86 years to circle the Sun."
"Phase Plane Analysis
and Observed Frozen Orbit
by Bruce E. Shapiro
"Frozen orbits exist at all inclinations,
even though they are frequently thought to exist
only for nearly-circular
nearly-polar and nearly-equatorial orbits
and at high eccentricity near the
(e.g. Molniya orbits)"
"In a more general sense,
can also refer to geo-synchronous
and sun-synchronous orbits."
[warning: throws around a bunch of Jacobian,
Hamiltonian, eigenvalues, and differential equations]
[Starts to analyze frozen orbits in general,
but leaves several details
"for further research"
when they don't apply to the focus of the paper,
the TOPEX mission].
"Existence of the frozen orbit
is usually attributed
to the balancing of the
secular pertubations of
even zonal harmonics
with the long period pertubations
of the odd zonal harmonics ...
zonal harmonics describing the
"Atmospheric drag ... should have
a stabilizing influence."
"... a continuous thrust
[from outgassing] can be either
stabilizing or destabilizing."
"Solar radiation pressure (SRP)
is the most significant non-gravitational
perturbation for TOPEX/Poseidon."
Due to higher order perturbations,
the elements describing an orbit actually change over time.
As an example, the fact that the Earth is not uniform
(and thus causes slightly different gravitational forces
at different places)
causes orbital elements to slowly change.
A frozen orbit
is one in which the orbital elements
have been chosen such that the average, or ‘mean’ elements remain very nearly constant.
these types of orbits minimize the effects that the non-spherical earth have on the orbital elements.
Other perturbations still impact the orbit,
however; some of which include: the gravitational effects of the sun and moon, drag effects, etc.
A Sun-synchronous orbit, which is free of eclipses, offers significant advantages for the power and thermal design of the spacecraft.
For a Sun-synchronous orbit,
the inclination is chosen as a function of semi-major axis and eccentricity
such that the node precession caused by the -flattening term in the gravity field
equals to the motion of the Sun relative to the planet.
The orbit altitude then has to be chosen above a minimum value
such that the spacecraft remains outside the shadow at the extreme cases
at the poles in mid-winter and mid-summer.
The orbit will always be near the terminator.
**The frozen orbit technique
uses carefully selected values of argument of perigee
(approximately 90 degrees) and eccentricity
the spacecraft mass will interact with the geopotential field
so that perigee rotation,
a familiar feature of ordinary near-circular low Earth-orbits,
is virtually eliminated.
With perigee rotation "frozen,"
the variation in instantaneous spacecraft altitude
is sharply restricted.
The required values of argument of perigee and eccentricity,
and the degree to which the altitude variation can be controlled,
vary with the orbital inclination.
In the case of UARS, the inclination was set at 57 degrees
due to science requirements.
DAV has read article
"Nanosatellites head for the launch pad"
by Stephen J. Mraz
_Machine Design_ magazine
info on Mark Tilden,
aesthetics, and mechanics" (BEAM)
A friend reading the sidebar
"A robot for every niche"
"Dress it like a lawyer.".
weigh less than 660 lb.
such as those being developed at Los Alamos,
tip the scales at 22 lb or less."
"Though many of their robots
Tilden and his team
believe the idea that robots
must be fashioned after biological forms
may be inherently flawed."
"The first nanosat
will use three torque coils, one per axis,
to orient itself in the Earth's magnetic field
and a photosensor pair
to point itself at the brightest available light source.
exploring the Van Allen radiation belt
Because they carry no microprocessors
or delicate electronics,
they are relatively immune to radiation."
"figuring out a way to get the information from the nanosats to Earth
without burdening the small spacecraft with the weight
of a large radio transmitter
or a power source to run it.
... possible solutions. Nanosats
designed to seek out magnetic minimums or maximums,
or some other celestial parameter, might
not need transmitters. They could be tracked
from Earth using radar or lasers ...
nanosats could modulate information
onto laser beams that bounce off them ...
small transmitter/receivers ... to a larger
mothership stationed near some point in the flock's orbit.
The mothership would then download the data to Earth.
each nanoset in the flock send a string of pulses at the same time.
The combined signal would be strong enough to be picked up
... on Earth."
"an outgrowth of work by Mark Tilden,
Jan Frigo, a senior research engineer
with expertise in adaptive control systems;
and Kurt Moore, an aerospace scientist."
The CubeSat Project
CubeSat Launches Now Available
Launches for November 2001 - 65 degree inclination, 600-800km
University - $30,000, Private - $45,000, Commercial - $60,000
Reservations required before February 15, 2001
has a interesting section
"Passive Techniques for Orbit Maintenance".
A classic example of engineers discovering some force
(not understanding what it is)
and turning it from a flaw into a feature.
(Has this force ever been explained ?)
**** Fastest-Spinning High-Energy Pulsar Discovered - UniSci
The fastest-spinning high-energy pulsar has been discovered,
whirling on its axis twice as fast as any similar star --
and six million times faster than the Earth.
Date: Tue, 15 Sep 1998 07:44:59 -0700 (PDT)
From: Kathryn Aegis <email@example.com>
To: firstname.lastname@example.org, email@example.com
Subject: >H SPACE:commercial spaceport opens in Virginia
Transhuman Mailing List
The first commercial rocket launching site was dedicated yesterday
(September 14, 1998) on Wallops Island, Virginia. Known as the Space
Flight Center, it was financed largely by private technology
corporations, with contributions from Virginia and federal funding
sources. Orbital Sciences expects to launch its Taurus series of
rockets from the 200-foot tower, and DynCorp and Lockheed Martin also
plan to utilize the site. The first launch should occur in the year 2000.
"The scientific world is buzzing with the suggestion
that signals from aliens living in another star system
may have been picked up by a part-time astronomer.
Other astronomers are scrambling to confirm or deny them.
It could either be the most important discovery ever made,
or more likely, a case of mistaken identity or an elaborate hoax."
Date: Wed, 24 Jun 1998 14:53:19 -0600 (MDT)
From: "Patrik D'haeseleer" <firstname.lastname@example.org>
Subject: fx-discuss: Earth2 news
The Extrasolar Planets Encyclopaedia announced the discovery of six more
possible Jupiter-sized planets (see http://wwwusr.obspm.fr/planets/). They
also list an article on a new technique which should make it possible
to detect Earth-size planets from Earth.
Preliminary observations of Betelgeuse, presented in San
Diego today, confirm the theoretical predictions of the mFTS's
performance. Although these test-bed observations, using a collecting
area only 12cm (5 inches) in diameter, are not sensitive enough to
detect Earth-sized planets around this particular bright star, the
results from the prototype instrument suggest that, for a telescope
3 meters (10 feet) in diameter, planets a few times the size of
the Earth could be detected around many of the stars visible to
the naked eye in the night sky.
Date: Thu, 2 Jul 1998 19:09:54 -0600 (MDT)
From: "Patrik D'haeseleer" <email@example.com>
Subject: Re: fx-discuss: Space Station claim looking for judge
Richard B. Woods writes:
>Already, some asteroids have been seen to pass closer to Earth than our
>Moon. I think the largest so far was about a half-mile wide.
Here's the relevant table: http://ssd.jpl.nasa.gov/ca_past.html
No. & Name, or Abs. Date of Close Distance Orbit
Designation Mag. Earth Approach (AU) (LD) Ref.
- ---------------- ---- -------------- ------ ---- --------
1994 XM1 28.0 1994-Dec-09.79 0.0007 0.3 JPL#3
1993 KA2 29.0 1993-May-20.86 0.0010 0.4 EB960803
1994 ES1 28.6 1994-Mar-15.72 0.0011 0.4 EB960110
1991 BA 28.7 1991-Jan-18.72 0.0011 0.4 EB960611
1996 JA1 20.5 1996-May-19.69 0.0030 1.2 JPL#7
1991 VG 28.8 1991-Dec-05.42 0.0031 1.2 JPL#4
1995 FF 26.4 1995-Apr-03.38 0.0045 1.8 EB960613
4581 Asclepius 20.5 1989-Mar-22.90 0.0046 1.8 EB960311
1994 WR12 22.2 1994-Nov-24.85 0.0048 1.9 EB960804
1937 UB (Hermes) 17.1 1937-Oct-30.71 0.0053 2.1 EB960619
1995 UB 26.8 1995-Oct-17.16 0.0050 1.9 EB960114
1993 UA 25.4 1993-Oct-18.80 0.0067 2.6 EB960618
1994 GV 27.5 1994-Apr-12.13 0.0068 2.6 EB960110
1993 KA 26.0 1993-May-17.93 0.0071 2.8 JPL#4
2340 Hathor 20.3 1976-Oct-20.74 0.0078 3.0 JPL#4
1988 TA 20.9 1988-Sep-29.09 0.0098 3.8 EB960817
LD refers to Lunar Distance, so the only four asteroids which are known
to have come closer than the Moon are 1994 XM1, 1993 KA2, 1994 ES1 and
1991 BA. Looking up the estimated diameter for those absolute magnitudes
(see http://cfa-www.harvard.edu/iau/lists/Sizes.html), we get sizes
between 4 and 15 meters, depending on albedo.
The article "What to do about bolts from the blue"
article by Steven Marcus
_IEEE Spectrum_ 1998-12
"1991VG may be a returning piece of manmade space debris."
"Asteroid and Comet Impact Hazards"
"Asteroids and Comets"
"Asteroid and Comet Defences"
"current efforts and future plans
to inventory and characterize the population of Near Earth Objects"
NEO detection programs:
Lowell Observatory Near-Earth Object Search (loneos)
Near-Earth Asteroid Tracking (NEAT)
Lincoln Near Earth Asteroid Research Project (Linear)
ODAS, the French-German Astroid Survey
Near Earth Asteroid Rendezvous (NEAR) mission
scheduled to achieve orbit around the near-earth asteroid 433 Eros
in 1999 Jan (?)
Life in Extreme Environments
"If life can exist somewhere - it will"
lots of cool articles about "extremophiles",
(creatures living in areas on Earth previously thought to be uninhabitable
by any living thing),
and the possibility of their survival on other planets and moons.
Archaea deep within the earth ("lithoautotrophic")
may comprise more than half of the earth's biomass;
fish and bacteria survive below 0 C at Antarctica;
creatures survive in complete darkness at temperatures above 150 C
at the bottom of the ocean;
"Methane Ice Worms" live and feed off solid chunks of CH4:H20;
"Archaea are "autotrophic," meaning that they subsist on carbon dioxide,
nitrogen and hydrogen -- they don't need any amino acids or pre-existing
Software detects small satellites in spacecraft imagery
Given a sequence of images ...
automatically detects small satellites of asteroids
and other planetary bodies ...
written in MatLab by
Paul Stolorz, Victoria Gor, and Richard Doyle of Caltech
Clark Chapman, Randy Gladstone, William Merline, and Alan Stern
of the Southwest Research Institute,
for NASA's Jet Propulsion Laboratory.
I've heard that Space Station Mir is visible to the naked eye;
anyone know how to figure out when and where to look ?
T a s t y B i t s f r o m t h e T e c h n o l o g y F r o n t
This issue: < http://www.tbtf.com/archive/03-02-98.html >
.Iridium puts on a light show
Getting our entertainment where we can find it
These low-earth-orbit satellites will enable worldwide phone ser-
vices beginning this year. Fifty-one are presently in orbit. It
turns out that the satellites' antennas catch the sun and cause
"flares"  visible from the ground. For minutes at a time the
satellites brighten from magnitude 6 (binoculars required) to
magnitude -2 or even -4 (brighter than Venus). This useful page
provided by the German Space Operations Centre  will calculate
for you the next seven Iridium flares visible from your location.
(Their initial mission was to calculate and display appearances of
the Mir satellite.) First you need to say exactly where on earth
you are. Using the Census Bureau's Tiger Mapping Service  you
can pinpoint a spot in the US to 4 decimal places of latitude and
longitude, or within about 6 feet. Start at this atlas of place
names  for rough coordinates that you can feed to the Tiger
TBTF home and archive at < http://www.tbtf.com/ >. To subscribe
send the message "subscribe" to firstname.lastname@example.org. TBTF
is Copyright 1994-1998 by Keith Dawson, < email@example.com >.
Commercial use prohibited. For non-commercial purposes please
forward, post, and link as you see fit.
closing the aperture down 1 stop ...
Exposure time should be doubled for each decrease in aperture.
moon photography falls into the category of snapshots.
A full moon, high in the sky,
requires an exposure of only about 1/250 second
on ISO 400 speed film with a lens set to f/16. A
quarter moon needs about 1/15 or 1/30 second with the same film speed
and lens aperture. ...
... the moon ... is only 1/2 degree in diameter. Using a
50 mm lens, its image on film measures a tiny 0.5 mm.
a focal length of 2400 mm is about the maximum
that can be used to capture the entire disk [on 24mm wide film].
Each 100 mm of focal length produces a lunar image of about 1 mm on film.
Focal lengths of 300 mm and longer can yield very vivid photographs.
The lower the moon and the denser the pollution,
the longer the exposure.
Except for snapshot photos of the sun and moon,
all forms of sky photography
that employ a telescope
require a drive mechanism in right ascension
and accurate polar alignment.
Super Secret Projects, Inc.
developed and sells OrbMaster(tm).
A Shareware version of OrbMaster(tm) is available for download.
"This new application allows the layman to understand spatial interactions, astronautical, astrodynamics, celestial events, orbital mechanics, and more."
lots of pretty interactive graphics.
what are cooling issues (thermal issues)
in satellite design ?
Other satellite design issues:
radiation (ionizing; ultraviolet; ...),
"The Space Environment and Effects (SEE) Program
collects, develops, and disseminates
the SEE-related technologies
required to design, manufacture and operate
more reliable, cost-effective spacecraft"
European Southern Observatory
astronomical observatories in Chile.
Has lots of pretty photos online.
the Near-Infrared Lab at the University of Rochester
has a gallery of pretty astronomical pictures,
some detailed photos of the infrared camera equipment,
and a few infrared pictures of more down-to-Earth subjects,
`` I am an astrophysicist (astronomy and physics),
currently working on development and testing of infrared array detectors
for NASA's Next Generation Space Telescope.''
Craig W. McMurtry.
Benjamin Franklin commenting on the anticipated arrival of Halley's Comet
(from Poor Richard's Almanack - 1757)
"Should a Comet in its Course strike the Earth, it might instantly beat it to Pieces, or
carry it off out of the Planetary System.
The great Conflagration may also, by Means of a Comet, be easily brought about. . . .
All the Disputes between the Powers of Europe would be settled in a Moment;
the World, to such a Fire, being no more than a Wasp's Nest thrown into an Oven.
"But our Comfort is, the same great Power that made the Universe, governs it by his Providence.
And such terrible Catastrophes will not happen till 'tis best they should.
-- In the mean time, we must not presume too much on our own Importance.
There are an infinite Number of Worlds under the divine Government, and
if this was annihilated it would scarce be missed in the Universe.
"God sees with equal Eye, as Lord of all,
A Hero perish, or a Sparrow fall.
Atoms, or Systems, into Ruin hurled,
And now a Bubble burst, -- and now a World!"