Space probe lands on comet in historic mission

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The three-legged lander had to be released at exactly the right time and speed because it could not be controlled on its descent. On its way down, Philae gathered data and images, which were relayed back to Earth.

Engineers designed the lander not knowing what type of terrain they would find on the comet’s surface. Rosetta has been taking pictures of the comet and collecting samples from its atmosphere as it approaches the sun, showing it is not as smooth as initially hoped, making landing more tricky.

via Space probe lands on comet in historic mission – Chicago Tribune.

From: Philae landing preview: What to expect on landing day

Philae’s legs are designed to damp out the forces of a hard landing to reduce the lander’s chance of bouncing. When Philae touches down, it will fire two harpoons to attach it firmly to the comet’s surface. A thruster on top of the lander fires at the same time as the harpoons, keeping the lander on the ground. Ice screws also deploy from the three lander feet.

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UPDATE: From Rosetta mission: Philae craft may have bounced during comet landing – as it happened

Philae may have landed not once but twice – that’s the final message from Esa this evening.

According to Stephan Ulamec, Philae Lander Manager, DLR, the lander team believe that Philae may have bounced from the surface and settled again in a slightly different place.

Rosetta to deploy lander on 12 November

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Two robust landing scenarios have been identified, one for the primary site and one for the backup. Both anticipate separation and landing on 12 November.

For the primary landing scenario, targeting Site J, Rosetta will release Philae at 08:35 GMT/09:35 CET at a distance of 22.5 km from the centre of the comet, landing about seven hours later. The one-way signal travel time between Rosetta and Earth on 12 November is 28 minutes 20 seconds, meaning that confirmation of the landing will arrive at Earth ground stations at around 16:00 GMT/17:00 CET.

via Rosetta to deploy lander on 12 November / Rosetta / Space Science / Our Activities / ESA.

Obama: Treat broadband—including mobile—as a utility

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In a plan released today, Obama said, “The time has come for the FCC to recognize that broadband service is of the same importance [as the traditional telephone system] and must carry the same obligations as so many of the other vital services do. To do that, I believe the FCC should reclassify consumer broadband service under Title II of the Telecommunications Act—while at the same time forbearing from rate regulation and other provisions less relevant to broadband services. This is a basic acknowledgment of the services ISPs provide to American homes and businesses, and the straightforward obligations necessary to ensure the network works for everyone—not just one or two companies.”

via Obama: Treat broadband—including mobile—as a utility | Ars Technica.

Reclassification of broadband service is almost certain to bring lawsuits from the telecommunications industry.

What is the difference between procedural programming and functional programming?

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I’ve read the Wikipedia articles for both procedural programming and functional programming, but I’m still slightly confused. Could someone boil it down to the core?

via glossary – What is the difference between procedural programming and functional programming? – Stack Overflow.

A functional language (ideally) allows you to write a mathematical function, i.e. a function that takes n arguments and returns a value. If the program is executed, this function is evaluated.

A procedural language, on the other hand, performs a series of sequential steps, where the functional program would be nested. There’s a way of transforming sequential logic into functional logic called continuation passing style.

As a consequence, a purely functional program always yields the same value for an input, and the order of evaluation is not well-defined; which means that uncertain values like user input or random values are hard to model in purely functional languages.

The Plane Crash That Gave Americans GPS

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The U.S. had already launched into orbit almost a dozen satellites that could help locate its military craft, on land, in the air, or on the sea. But the use of the system was restricted. (It was meant, for instance, to help powerful weapons hit their targets—it wasn’t the sort of tool governments usually want to make publicly available.) Now, Reagan said, as soon as the next iteration of the GPS system was working, it would be available for free.

It took more than $10 billion and until over 10 years for the second version of the U.S.’s GPS system to come fully online. But in 1995, as promised, it was available to private companies for consumer applications. Sort of. The government had built in some protection for itself—”selective availability,” which reserved access to the best, most precise signals for the U.S. military (and anyone it chose to share that power with).

via The Plane Crash That Gave Americans GPS – The Atlantic.

One wi-fi hotspot for every 150 people, says study

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Over the next four years, global hotspot numbers will grow to more than 340 million, the equivalent of one wi-fi hotspot for every 20 people on earth, the research finds.

via BBC News – One wi-fi hotspot for every 150 people, says study.

“At the moment you have to have a separate log-in for every hotspot and ultimately the winning providers are those that will offer the easier access experience,” she said.

Top Open-Source Static Site Generators

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The typical CMS driven website works by building each page on-demand, fetching content from a database and running it through a template engine. This means each page is assembled from templates and content on each request to the server.

For most sites this is completely unnecessary overhead and only ads complexity, performance problems and security issues. After all, by far the most websites only change when the content authors or their design team makes changes.

A Static Site Generator takes a different approach and generate all the pages of the website once when there’s actually changes to the site. This means there’s no moving parts in the deployed website. Caching gets much easier, performance goes up and static sites are far more secure.

via Top Open-Source Static Site Generators – StaticGen.

Archiving command history in Linux

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#!/bin/bash
 umask 077
 max_lines=10000
 linecount=$(wc -l < ~/.bash_history)
 if (($linecount > $max_lines)); then
         prune_lines=$(($linecount - $max_lines))
         head -$prune_lines ~/.bash_history >> ~/.bash_history.archive \
                && sed -e "1,${prune_lines}d"  ~/.bash_history > ~/.bash_history.tmp$$ \
                && mv ~/.bash_history.tmp$$ ~/.bash_history
 fi

via BashFAQ/088 – Greg’s Wiki.

I needed to manage shell command history in a formal fashion in order to turn repeated sequences into scripts without having to type them in again.  I also wanted a  record of packages installed and in what order.   The history of commands is contained in .bash_history file which is read once when a terminal opens.   Running set -o vi allows for history commands to be recalled using standard vi commands.  The above script can be run as a user level cron job to periodically prune the top so many commands and place them into an archive.

The bash statements below set history size and make it so a command will be written to the history file immediately and not simply when a terminal closes.   These should be placed in .bashrc or whatever file executes when a new terminal opens.

HISTFILESIZE=400000000
HISTSIZE=10000
PROMPT_COMMAND="history -a"
export HISTSIZE PROMPT_COMMAND

shopt -s histappend