CCNet, 33/2003 -  21 March 2003

Historical records of solar activity indicate that solar radiation has been increasing
since the late 19th century. If a trend, comparable to the one found in this study,
persisted throughout the 20th century, it would have provided a significant component of
the global warming the Intergovernmental Panel on Climate Change reports to have occurred
over the past 100 years."
--Richard Willson, NASA Goddard Institute for Space Studies

"Fear and hope are the two great motivators of human action, and neither untempered by the other leads to wise decision-making. Paralysis by unreasonable fear is as much to be avoided as the foolhardiness induced by groundless hope; but, of the two, fear is the more easily generated. It is certainly more common nowadays than unbounded optimism."
--The Spectator, 22 March 2003




    NEO Information Centre, 20 March 2003

    ESA, 21 March 2003

    SpaceDaily, 19 March 2003

    Andy Smith <>

    The Spectator, 21 March 2003



Elvia H. Thompson
Headquarters, Washington            March 20, 2003
(Phone: 202/358-1696)

Krishna Ramanujan
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-3026)

RELEASE: 03-106


Since the late 1970s, the amount of solar radiation the sun emits, during times of quiet sunspot activity, has increased by nearly .05 percent per decade, according to a NASA funded study.

"This trend is important because, if sustained over many decades, it could cause significant climate change," said Richard Willson, a researcher affiliated with NASA's Goddard Institute for Space Studies and Columbia University's Earth Institute, New York. He is the lead author of the study recently published in Geophysical Research Letters.

"Historical records of solar activity indicate that solar radiation has been increasing since the late 19th century. If a trend, comparable to the one found in this study, persisted throughout the 20th century, it would have provided a significant component of the global warming the Intergovernmental Panel on Climate Change reports to have occurred over the past 100 years," he said.

NASA's Earth Science Enterprise funded this research as part of its mission to understand and protect our home planet by studying the primary causes of climate variability, including trends in solar radiation that may be a factor in global climate change.

The solar cycle occurs approximately every 11 years when the sun undergoes a period of increased magnetic and sunspot activity called the "solar maximum," followed by a quiet period called the "solar minimum."

Although the inferred increase of solar irradiance in 24 years, about 0.1 percent, is not enough to cause notable climate change, the trend would be important if maintained for a century or more. Satellite observations of total solar irradiance have obtained a long enough record (over 24 years) to begin looking for this effect.

Total Solar Irradiance (TSI) is the radiant energy received by the Earth from the sun, over all wavelengths, outside the atmosphere. TSI interaction with the Earth's atmosphere, oceans and landmasses is the biggest factor determining our climate. To put it into perspective, decreases in TSI of 0.2 percent occur during the weeklong passage of large sunspot groups across our side of the sun. These changes are relatively insignificant compared to the sun's total output of energy, yet equivalent to all the energy that mankind uses in a year. According to Willson, small variations, like the one found in this study, if sustained over many decades, could have significant climate effects.

In order to investigate the possibility of a solar trend, Willson needed to put together a long-term dataset of the sun's total output. Six overlapping satellite experiments have monitored TSI since late 1978. The first record came from the National Oceanic and Atmospheric Administration's
(NOAA) Nimbus7 Earth Radiation Budget (ERB) experiment (1978 - 1993). Other records came from NASA's Active Cavity Radiometer Irradiance Monitors: ACRIM1 on the Solar Maximum Mission (1980 - 1989), ACRIM2 on the Upper Atmosphere Research Satellite (1991 - 2001) and ACRIM3 on the ACRIMSAT satellite (2000 to present). Also, NASA launched its own Earth Radiation Budget Experiment on its Earth Radiation Budget Satellite (ERBS) in 1984. The European Space Agency's (ESA) SOHO/VIRGO experiment also provided an independent data set (1996 to 1998). 

In this study, Willson, who is also Principal Investigator of NASA's ACRIM experiments, compiled a TSI record of over 24 years by carefully piecing together the overlapping records. In order to construct a long-term dataset, he needed to bridge a two-year gap (1989 to 1991) between
ACRIM1 and ACRIM2. Both the Nimbus7/ERB and ERBS measurements overlapped the ACRIM 'gap.' Using Nimbus7/ERB results produced a 0.05 percent per decade upward trend between solar minima, while ERBS results produced no trend. Until this study, the cause of this difference, and hence the validity of the TSI trend, was uncertain. Willson has identified specific errors in the ERBS data responsible for the difference. The accurate long-term dataset, therefore, shows a significant positive trend (.05 percent per decade) in TSI between the solar minima of solar cycles 21 to 23 (1978 to present). This major finding may help climatologists to distinguish between solar and man-made influences on climate.

NASA's ACRIMSAT/ACRIM3 experiment began in 2000 and will extend the long-term solar observations into the future for at least a five-year minimum mission.

For more information on the Internet, visit:

For more information about ACRIM on the Internet, visit:


>From, 20 March 2003

By Robert Roy Britt

In what could be the simplest explanation for one component of global warming, a new study shows the Sun's radiation has increased by .05 percent per decade since the late 1970s.

The increase would only be significant to Earth's climate if it has been going on for a century or more, said study leader Richard Willson, a Columbia University researcher also affiliated with NASA's Goddard Institute for Space Studies.

The Sun's increasing output has only been monitored with precision since satellite technology allowed necessary observations. Willson is not sure if the trend extends further back in time, but other studies suggest it does. 
The recent trend of a .05 percent per decade increase in Total Solar Irradiance (TSI) in watts per meter squared, or the amount of solar energy that falls upon a square meter outside the Earth's atmosphere. The trend was measured between successive solar minima that occur approximately every 11 years. At the bottom, the timeline of the many different datasets that contributed to this finding, from 1978 to present.

"This trend is important because, if sustained over many decades, it could cause significant climate change," Willson said.

In a NASA-funded study recently published in Geophysical Research Letters, Willson and his colleagues speculate on the possible history of the trend based on data collected in the pre-satellite era.

"Solar activity has apparently been going upward for a century or more," Willson told today.

Significant component

Further satellite observations may eventually show the trend to be short-term. But if the change has indeed persisted at the present rate through the 20th Century, "it would have provided a significant component of the global warming the Intergovernmental Panel on Climate Change reports to have occurred over the past 100 years," he said.

That does not mean industrial pollution has not been a significant factor, Willson cautioned.

Scientists, industry leaders and environmentalists have argued for years whether humans have contributed to global warming, and to what extent. The average surface temperature around the globe has risen by about 1 degree Fahrenheit since 1880. Some scientists say the increase could be part of natural climate cycles. Others argue that greenhouse gases produced by automobiles and industry are largely to blame.

Willson said the Sun's possible influence has been largely ignored because it is so difficult to quantify over long periods.

Confounding efforts to determine the Sun's role is the fact that its energy output waxes and wanes every 11 years. This solar cycle, as it is called, reached maximum in the middle of 2000 and achieved a second peak in 2002. It is now ramping down toward a solar minimum that will arrive in about three years.


Changes in the solar cycle -- and solar output -- are known to cause short-term climate change on Earth. At solar max, Earth's thin upper atmosphere can see a doubling of temperature. It swells, and denser air can puff up to the region of space where the International Space Station orbits, causing increased drag on the ship and forcing more frequent boosts from space shuttles.

Changing Sun 

Solar max has also been tied to a 2 percent increase in clouds over much of the United States.

It might seem logical to assume tie climate to solar output, but firm connections are few. Other studies looking further back in time have suggested a connection between longer variations in solar activity and temperatures on Earth.

Examinations of ancient tree rings and other data show temperatures declined starting in the 13th Century, bottomed out at 2 degrees below the long-term average during the 17th Century, and did not climb back to previous levels until the late 19th Century. Separate records of sunspots, auroral activity (the Northern Lights) and terrestrial deposits of certain substances generated in atmospheric reactions triggered by solar output, suggest the Sun was persistently active prior to the onset of this Little Ice Age, as scientists call the event.

Solar activity was lowest during the 17th Century, when Earth was most frigid.

Large-scale ocean and climate variations on Earth can also mask long-term trends and can make it difficult to sort out what is normal, what is unusual, and which effects might or might not result from shifts in solar radiation.

To get above all this, scientists rely on measurements of total solar energy, at all wavelengths, outside Earth's atmosphere. The figure they derive is called Total Solar Irradiance (TSI).

Heating up

The new study shows that the TSI has increased by about 0.1 percent over 24 years. That is not enough to cause notable climate change, Willson and his colleagues say, unless the rate of change were maintained for a century or more.

On time scales as short as several days, the TSI can vary by 0.2 percent due to the number and size of sunspots crossing the face of the Sun. That shift, said to be insignificant to weather, is however equal to the total amount of energy used by humans, globally, for a year, the researchers estimate.

The study analyzed data from six satellites orbiting Earth at different times over the 24 years. Willson ferreted out errors in one of the datasets that had prevented previous studies from discovering the trend.

A separate recent study of Sun-induced magnetic activity near Earth, going back to 1868, provides compelling evidence that the Sun's current increase in output goes back more than a century, Willson said.

He said firm conclusions about whether the present changes involve a long-term trend or a relatively brief aberration should come with continued monitoring into the next solar minimum, expected around 2006.

Copyright 2003,


>From, 21 March 2003,2106,2346810a11,00.html

Space junk or big meteor? Whatever it was, the big, bright light that hurtled northward over an area from Nelson to Palmerston North in the early morning light of Wednesday was according to witnesses "really honking".

Fifteen sightings were reported to the Carter Observatory and astronomer Brian Carter said the object was probably man-made space junk.

But Noel Munford, of the Manawatu Astronomical Society, said the international astronomical website that reliably tracks bigger pieces of space debris had given no warning of a significant object coming in.

Witnesses had reported the object was travelling at great speed across the sky and did not break up, as space debris usually did.

That suggested the object was a "bolide" - a meteor far bigger that the usual pea- or pebble-sized "shooting star". And it might have disappeared because it came in at a low angle and skimmed off the upper atmosphere back into space.


>From NEO Information Centre, 20 March 2003

Today at the Lunar and Planetary Science Conference in Houston Dr Jim Head presented new results to suggest that about one rock from Mars falls on Earth each month. Head's work involves calculating exactly how often asteroids and comets impact with the planet Mars and how many martian rocks these collisions blast up into space. He then models the paths of these little fragments of the red planet, under the influence of the combined gravity of the planets and Sun to see how many and how often such martian meteorites fall to Earth.

The results of the new research suggest that martian meteorites come from craters larger than 3 km on the red planet and take up to 100 million years to make the 45 million kilometre journey to the Earth. Head's work implies that the currently known martian meteorites, of which there are just over 20, come from around 6 craters on the martian surface and so some are samples of closely related rocks that can give additional clues to the geological history of the red planet.

Martian meteorites are our only samples of another planet and they provide us with the opportunity of to investigate how planets form and evolve in general. It is only because of the collision of asteroids and comets with Mars, every few hundred thousand years, that we can study the red planet in such detail.


>From ESA, 21 March 2003

ESA INFO 06-2003. Following the decision not to launch Europe's comet chaser Rosetta in January, scientists and engineers in the programme have been examining several alternative mission scenarios.
Each has been looked at on the basis of the expected scientific return, the technical risks related to using the Rosetta design in the new mission, and the containment of costs. Of the nine mission scenarios studied by the Rosetta Science Working Team, three have survived to this point and were presented to the delegations of the ESA Member States through the Science Programme Committee at its meeting on 25/26 February. Two mission scenarios (in February 2004 and 2005 respectively) would take Rosetta to a new target comet, Churyumov-Gerasimenko, while another (in January 2004) would take it to its original target, Comet Wirtanen.

All three options are now being studied in detail so that the final decision can be made. A campaign of observations using both the NASA/ESA Hubble Space Telescope and the instruments of the European Southern Observatory is under way to study Comet Churyumov-Gerasimenko. In this way, astronomers will be able to characterise the comet and perform a mission analysis, also to identify landing scenarios and make a thorough assessment of any hardware modification that would be necessary.

In parallel, ESA is assessing the launch requirements for the various mission scenarios. This will include looking at alternatives to Ariane as back-up options, such as the Russian Proton rocket.

The final decision on Rosetta's new mission scenario will be made by the ESA Science Programme Committee in May.

Note to editors

Following the failure of Ariane Flight 157 in December with the loss of two spacecraft, ESA and Arianespace took the joint decision not to launch Rosetta during its January launch window. This meant that Rosetta's originally intended mission to Comet Wirtanen had to be abandoned.

For more information please contact:

ESA Communication Department
Media Relations Service, Paris, France
Tel: +33(0)15369 7155
Fax: +33(0)1 5369 7690


>From SpaceDaily, 19 March 2003

by Marc D. Rayman
Dawn Project Engineering Team
Jet Propulsion Laboratory

Pasadena - Mar 19, 2003
The design of Dawn's trajectory is difficult, unusual, and interesting because of the use of solar electric propulsion, implemented on Dawn as an ion propulsion system (IPS).

While providing performance far in excess of what conventional chemical propulsion would deliver, the IPS necessitates the use of design tools and methods quite different from what has been used for the development of trajectories since the dawn of the solar system (or, at least, since the dawn of space exploration).

Rather than finding a few points at which impulsive maneuvers are required, this problem involves the determination of IPS thrust vectors over years of continuous thrusting.

Unlike trajectories for ballistic missions, Dawn's depends sensitively on the spacecraft's power system (because power translates directly into IPS thrust). The tools that generate the trajectories require much more coaxing and cajoling (and sometimes pleading) than the tools that have been used for conventional missions.

In addition to the different underlying mathematical problem, the use of the IPS necessitates unfamiliar constraints on the mission. For example, because IPS thrusting is needed for years at a time, the mission could be vulnerable to an unexpected loss of thrust.

Therefore, a substantial effort is devoted to designing a trajectory with enough "mission margin" that most spacecraft problems that interfere with IPS thrusting do not jeopardize reaching both Vesta and Ceres. (Missions relying on chemical propulsion tend to have greater vulnerability for shorter times.)

The initial work is focused on obtaining an understanding of the sensitivity of the trajectory to parameters that we can control.

Ultimately we will develop a baseline trajectory that accounts for constraints such as the finite launch period, launch window, Vesta arrival window (to ensure good lighting for framing camera and mapping spectrometer observations of the south pole), Ceres arrival window (for lighting at one of the poles), mission margin, periods in which spacecraft activities preclude thrusting in the optimal direction, spacecraft power characteristics, flybys of other asteroids during the interplanetary cruise, and others.

We separately analyze the orbit insertion, departure, and orbit transfers at each primary science target, where the complexity of spiraling around the bodies requires different analytical techniques.

Steve Williams and Dr. Greg Whiffen of JPL are the principal trajectory analysts on Dawn. Steve designed the trajectory for Deep Space 1 (DS1), the mission that tested the IPS design Dawn uses. Many issues that an operational IPS flight would face were revealed during that work; prior analyses had rarely, if ever, exceeded the depth necessary for conceptual studies.

Greg has written a powerful new trajectory design tool that complements the one used for DS1. With his new software, Greg has generated our first looks at the Vesta orbit transfers. The first baseline trajectory will be completed by early April. Although preliminary, it will be significantly more accurate than previous calculations.



>From Andy Smith <>

Hello Benny and CCNet,

This note is to announce that we are expanding our ACE scale to add objects smaller than Tunguska (ACE#1) and larger than Hale-Bopp (ACE#10). Our scale is an exponential step-scale, which doubles the NEO diameter with each increasing step. The log. of the released destructive impact energy (megatons of TNT) is about the same as the step number and the log. of the interval between impacts (years) is approximately the same as the step number plus one.

The extension, on the low-end of the scale, will go down to slightly under a meter (ACE#-5). On the high end, it will increase to an NEO width of about 100 kilometers (ACE#12).

We are also adding comparison scales, to include the Richter Scale(RS) and the Volcanic Explosivity Index (VEI). All three are exponential magnitude step-scales. Our pivotal event, the
Tunguska/Arizona/Mt. St. Helens level event (ACE#1) is about equal to #6.5 on the RS and #5, on the VEI. The level #10 events, on the other two scales, are about the same as our ACE#6 (impact of a 1.6 kilometer ball).

We find crater-size a useful basis for comparison, between the ACE and the VEI. 

We are also re-examining the energy level associated with the ACE#1 event, because the Arizona
(Barringer)crater seems much too large for a 10-20 megaton explosion. The energy level of this event, we think, may have been well in excess of 50 megatons.

We still think a short regional winter (like the one associated with the Tambora volcanic explosion)could result from an ACE#3-#4 impact (200-400 meters) and that the duration and severity would increase, with increasing NEO size.

Fortunately, most of the NEO threat population is smaller than ACE#4 (about abs.magnitude 19.5) . It is for this reason, that we feel the next generation of NEO telescopes is so important and we are still urging the larger, more advanced available survey units/teams (like the SLOAN and the NEWTON) to help more, with the search.


Andy Smith/IPPA


>From The Spectator, 21 March 2003

Fear and hope are the two great motivators of human action, and neither untempered by the other leads to wise decision-making. Paralysis by unreasonable fear is as much to be avoided as the foolhardiness induced by groundless hope; but, of the two, fear is the more easily generated. It is certainly more common nowadays than unbounded optimism.

How easily unfounded fear is provoked has been demonstrated this week by the appearance of a new disease in China of unknown causation. No sooner had nine people died of it, out of a global population of six billion, than the end of the world, or at least of humanity, was deemed in certain quarters to be nigh: and this despite the fact that the great majority of the people who have contracted the disease have survived it, not died from it.

Nothing is easier to conjure up from the unknowability of the future than panic. There is no difficulty in imagining the most terrible of consequences from the most banal of actions, let alone from genuinely dangerous ones. Certain minds take pleasure in predicting apocalypses, and the failure of the last predicted apocalypse to make its appearance at the duly appointed time never reduces the certainty with which the next apocalypse is envisioned.

Because the future is inherently unknowable, and because dramatic predictions are so much more vivid in our minds than undramatic ones, the Cassandras of the world enjoy a certain natural advantage, which has nothing to do with their accuracy or clairvoyance. A book predicting disaster will always sell more than one which predicts that the world will continue in its chronically unsatisfactory but nevertheless survivable way.

This should be borne in mind when the possible consequences of the war with Iraq are discussed. The person who says that it will result in eternal enmity between the Middle East and the West, and in ever more terrorism directed at Western cities, will be paid more attention than one who predicts less fraught consequences, simply because what the former says is more arresting. Our desire to be entertained is generally greater than our thirst for truth; and apocalypses are nothing if not entertaining.

Eventually, decisions have to be made and risks taken. The risks involved in making war on Iraq are now slight because the armed forces arrayed against it are so formidable. Moreover, it is unlikely that many Iraqis will wish to go to their deaths to fight for Saddam Hussein and his small clique of thugs. No one can be absolutely sure of this, of course, and perhaps Iraqi civilians will turn out to be ferocious urban guerrillas. But if we seriously entertained such outside possibilities in our daily lives, we would make Hamlet seem impulsive and unreflective.

As for the undying enmity that making war on Iraq will supposedly generate, it assumes not only that, uniquely among large populations of human beings, unanimity of opinion exists in the Middle East, but also that those in the Middle East who do indeed hate us will hate us less than they do if we refrain from making war on Iraq. This is highly doubtful, to say the least; it assumes that we are hated for what we do rather than for what we are and what we represent. A withdrawal from war would not now make us more loved, or even less hated; it would simply make us ridiculous.

For every fearful vision of the future, there is an equal and opposite fearful vision. The epidemic in China could, if it evoked an exaggerated response, bring about a collapse in world trade, as China and South-east Asia were sealed off or quarantined from the rest of the world. If Saddam were not checked now, his successful defiance of the most powerful country in the world would set an example for many aspiring regional despots to follow, and in the end would result in many small nuclear wars.

One of the problems with pre-emptive action is that what has been pre-empted can never be known for certain, while the undesired effects - what the Americans call collateral damage - can be assessed retrospectively with some degree of accuracy. On this view, pre-emptive action is never justified; for only collateral damage is certain.

Prudence, the greatest of all political virtues, shades imperceptibly into timidity and outright cowardice. Fearful imaginings can always be made a reason for doing nothing, or for retreating into a world of one's own. The agoraphobic refuses to go out because he is prey to fears of what might happen to him once he leaves the safety of his domestic cocoon, though of course sometimes unpleasant things do happen to people who leave their homes. But if everyone were agoraphobic, the human race would soon die out, for no one would produce or distribute anything. The world needs nations, as well as men, who are unafraid.

The choice before humans is never between risk and no risk; it is always between different risks. The risks of making war are now far outweighed by those of not making war. And the only thing we have to fear is fear itself.

Copyright 2003, The Spectator

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