A Day Without Satellites

The BBC has a short fictional piece about what would happen if all the world’s satellites stopped working. While that is unlikely, it’s an interesting look at how much satellites are integrated into everyday technology. For instance, while the Internet is mostly an Earth-based affair with undersea cables connecting continents, I didn’t know that that the atomic clocks on GPS satellites were used by data centers and Internet exchange points to timestamp Internet data packets. One thing I’m a bit confused by is how much the article claims international telephone calls would be disrupted. I could see things like aid workers and military units who are in areas with little landline or mobile infrastructure being affected, but I thought most international calls on landlines and regular cell phones were done through the undersea cable network.

While this article may be drastic, it is important to note that our satellites are increasingly at risk of damage and it’s an issue that increasingly concerns industry and governments.

Obama’s Science Record

Nature recently published a lengthy article in their news section that looks at how well President Obama kept his promise to “value science” in his administration.  The opinion seems to be that, for the most part, he lived up to his word.  Over four years, I’ve forgotten what a big deal most of his science policy nominees were and how much respect they garnered from colleagues in his field.  And I have no way of comparing it to George W. Bush’s administration, but I also remember hearing about the big push by the incoming Obama administration to hire researchers for various executive appointments.  One of my science professors freshman year mentioned how faculty at our university had gotten several invitations to apply for executive agencies.  

And his rock star science team seems to have done well, mostly.  A common complaint about Bush-era science agencies was that the White House would “muzzle” researchers when their data or policy suggestions contrasted with the administration’s goals.  One of Obama’s promises was to require federal agencies to develop “scientific integrity” policies that would ensure scientists could state their own views and publish their own data without political interference.  It took a bit longer than expected to create all these policies, but now they’re nearly all in place.

Of course, any mention of the integrity policies would be incomplete without mentioning the two big controversies on this end.  During the Deepwater Horizon oil spill, US Geological Survey employees complained that the Obama administration pressured them to underestimate the amount of oil in the Gulf.  And an initial estimate from NOAA was criticized for being done by someone with no experience in the area and using poor techniques.

And at the end of last year, there was some large intramural fighting in the administration.  The Food and Drug Administration’s Center for Drug Evaluation and Research recommended that the morning-after pill, Plan B, be made available to all girls “over the counter”.  The Secretary of Health and Human Services, Kathleen Sebelius, overruled that decision and kept the current policy requiring a prescription for girls under 17 in place.  In a memo, Sebelius claimed that there is not enough evidence showing that the “youngest girls of reproductive age” could safely use Plan B on their own.  The bigger deal was the follow-up, though.  FDA Commissioner Margaret Hamburg fought back in her public statement said that she agreed with the Center’s review.

There’s also lots of other things that happened over the last four years:  science spending in the stimulus, NASA, various proposals to open up new land to resource extraction and also new regulations, the development of ARPA-E, and the list goes on.  But the Nature piece already does a good job, and I don’t see a need to rehash everything they say.  So go check it out.

Tweets from Space

In honor of the Curiosity rover landing on Mars in less than 24 hours (knock on wood), why not check in on its tweets to see how it feels?  You read that right.  NASA has set up a Twitter account for the Curiosity rover.  I was about to declare this the first ever official Twitter for a scientific experiment (while CERN has an account, it’s for the entire organization, and all the LHC accounts are made by enthusiasts).  However, it turns out Mars tweets are old hat for NASA, which set up an account for the Phoenix mission back in 2008.

Since robotic intelligence is not advanced enough yet for space rovers to actually talk to us, @MarsPhoenix and @MarsCuriosity are actually run by NASA’s social media team.  But it looks like they hope to have updates in almost real time as Curiosity gets ready for major milestones (at posting time, Curiosity last reported getting closer to Mars than the moon is to Earth).

I think these Twitter accounts are great moves by NASA.  Twitter’s character limit is a great way to send bite-sized mission updates to the broader public, and judging by its follower count, people love it.  Sometimes science in social media gets a bit of flak (I remember a few people saying the CDC’s zombie comic was a money waster), but I’m all for new ways to reach out to the public.  Important results should be vetted by peers before we accept things as fact, and the CDC comic was really only super helpful if you read the emergency preparedness guide with it, but there’s nothing wrong with getting people to care about this stuff in the first place by giving them a taste of excitement.

Hat tip:  Mars Orbited Adjusts, Rover Gets Twitter Account from Greg Laden on Science Blogs

O Pioneers!

Some practically ancient technology has recently been used to rule out some exotic theories of physics.  The Pioneer 10 and 11 probes, which were the first successful space missions to Jupiter and Saturn, respectively, have still provided data since their launch in the 1970s.  After the Pioneers observed their target planets, they still transmitted radio signals back to Earth, and NASA would also try to bounce radio waves off the probes.  Similar to how you can tell if an ambulance or train is rushing towards you or moving away by the change in pitch, NASA could use the Doppler effect to measure the velocity of the probes along their paths.

Astronomers wanted to use this data to study the influence of gravity farther out in the solar system, where the mass of the Sun and outer planets wouldn’t overwhelm smaller effects.  Of course, studying “small effects” in deep space required accounting for many variables.  John Anderson, the lead analyst of the Doppler data, started to notice small differences between his model’s predictions and the Pioneers’ actual velocity and position data beyond Neptune’s orbit.  The probes were experiencing a small acceleration towards the Sun, slowing them down.  By small, they mean really small:  the acceleration was calculated as being 8.74 x 10-10 meters per second per second.  (To help put that in context, it would take over 400 years of constant acceleration of that amount to get up to the average person’s walking speed)

For the probes to be experiencing that acceleration means they need to be experiencing some sort of force.  Anderson’s team originally wrote it off as unexpected gas leaks from the Pioneers’ thrusters.  But the anomalous acceleration persisted even after the thrusters should have run out of fuel.  And that started to concern astronomers.  Anderson’s model accounted for all known gravitational sources in the outer solar system, and even more complicated effects such as radiation pressure from the Sun.  So something astronomers didn’t know about must have been the cause of the anomaly.

Astronomers and physicists have come up with dozens of interesting explanations for the Pioneer anomaly that would change our understanding of the universe.  Some have proposed previously unknown clusters of dark matter in the solar system, but this was ruled out when the Voyager probes never showed this acceleration and our models of planetary orbits never showed such problems.  Others proposed rewriting gravity.  Ironically, an alternative theory to dark matter, known as Modified Newtonian dynamics (or MOND) was also invoked to explain the anomaly, as it proposes that gravity behaves differently at extremely low accelerations (intriguingly, also on the order of 10 to -10 meters per second per second).  Others proposed that time passed at different rates for objects depending on their acceleration through the gravitational field of space, and Anderson’s group actually considered these theories for a while (in some way I truly don’t understand).

And others proposed less exciting explanations.  Tiny amounts of gas could be produced and leak from the Pioneer’s nuclear power sources.  And some thought even the tiny amounts of heat radiating off the probes could cause push the probes off course.   No one seems to have taken the gas theory very seriously.  And Anderson’s team (now working with Slava Turyshev) wrote off the heat theory in the early 2000s, saying any force based on the heat should have decreased with distance from the sun.

Viktor Toth, a programmer who seems to do theoretical physics in his free time (seriously), helped change their minds.  Toth argued that Anderson’s team couldn’t rule out thermal effects unless they did a detailed analysis.  In an interesting story showing the merits of preserving old research data, Toth helped Turyshev save or find copies of nearly all the Pioneer mission’s Doppler and temperature telemetry.  Somewhat amazingly, the team (now with Toth) managed to recreate a full CAD model of Pioneer 10 based on the original engineering drawings and using the temperature data, ran a computer simulation measuring the thermal emissions in all directions.  Their model showed that the radiation could be responsible for all but about 20% of the acceleration.

The model seems pretty convincing.  But their figures look like they show the “thermal recoil” effect decreasing further from the sun, while the anomaly still seems constant.  So maybe there’s still room for some anomalous physics.