Archive for September, 2009

The following pictures and details were posted on NASA’s website.

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These images show a very young lunar crater on the side of the moon that faces away from Earth, as viewed by NASA’s Moon Mineralogy Mapper on the Indian Space Research Organization’s Chandrayaan-1 spacecraft. On the left is an image showing brightness at shorter infrared wavelengths. On the right, the distribution of water-rich minerals (light blue) is shown around a small crater. Both water- and hydroxyl-rich materials were found to be associated with material ejected from the crater.

Credits: ISRO/NASA/JPL-Caltech/USGS/Brown Univ.

 

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This image of the moon is from NASA’s Moon Mineralogy Mapper on the Indian Space Research Organization’s Chandrayaan-1 mission. It is a three-color composite of reflected near-infrared radiation from the sun, and illustrates the extent to which different materials are mapped across the side of the moon that faces Earth.
Small amounts of water and hydroxyl (blue) were detected on the surface of the moon at various locations. This image illustrates their distribution at high latitudes toward the poles.
Blue shows the signature of water and hydroxyl molecules as seen by a highly diagnostic absorption of infrared light with a wavelength of three micrometers. Green shows the brightness of the surface as measured by reflected infrared radiation from the sun with a wavelength of 2.4 micrometers, and red shows an iron-bearing mineral called pyroxene, detected by absorption of 2.0-micrometer infrared light.

Image credit: ISRO/NASA/JPL-Caltech/Brown Univ./USGS

 

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These graphs show detailed measurements of light as a function of color or wavelength. The data, called spectra, are used to identify minerals and molecules. On the left are spectra of lunar rocks, minerals and soil returned to Earth by NASA’s Apollo missions, taken in the visible to shorter-wavelength infrared range. The blue bar shows where a dip in the light is expected due to the presence of water and hydroxyl molecules. To the left are model spectra for pure water (H2O) and hydroxyl (OH-).

Image credit: ISRO/NASA/JPL-Caltech/Brown Univ.

 

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These images from NASA’s Moon Mineralogy Mapper on the Indian Space Research Organization’s Chandrayaan-1 spacecraft show data for the hemisphere of the moon that faces Earth. The image on the left shows albedo, or the sunlight reflected from the surface of the moon. The image on the right shows where infrared light is absorbed in the characteristic manner that indicates the presence of water and hydroxyl molecules. That image shows that signature most strongly at the cool, high latitudes near the poles. The blue arrow indicates Goldschmidt crater, a large feldspar-rich region with a higher water and hydroxyl signature.

Image credit: ISRO/NASA/JPL-Caltech/Brown Univ.

 

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Many small, fresh craters bear signatures of water and hydroxyl, which are detected as absorptions of infrared light in the range of 3 micrometers by NASA’s Moon Mineralogy Mapper. Figure A, on the left, shows feldspar-rich terrain on the side of the moon facing away from Earth. The arrows point to the location of small, fresh craters. Figure B, on the right, indicates the reflectance as a function of wavelength for craters in Figure A. The water and hydroxyl signature in these regions is seen as a characteristic dip in reflectance in the infrared light near the 3-micrometer range, a region noted with a light-blue band. The dashed line shows background soil that doesn’t contain significant water or hydroxyl.

Image credit: ISRO/NASA/JPL-Caltech/Brown Univ.

India’s maiden moon mission which terminated prematurely is now showing results which support’s ISRO’s claim of mission success.

Moon Chandrayaan-1, India’s mission to moon has found damp soil which confirms the existence of water near the polar regions of the moon. The Royal Astronomical Society (RAS) calls this as a major breakthrough that international space scientists were waiting for in order to kick start the moon exploration program again.

The discovery was made using a Moon Mineralogy Mapper (M3) instrument built by NASA to go onboard Chandrayaan-1. It is being thought that considerable deposits of water could be available around the poles of the moon. Speculations are on that moon has 1 litre of water in every tonne of soil.

This can be a very important discovery for the future of space missions as the moon can now serve as a base for the future deep space explorations. It is relatively easy to extract oxygen from water molecules and this oxygen can be useful to sustain life on moon for longer durations or to fuel the long distance rockets. Also building a space station can be relatively cheaper as compared to building and sustaining the International Space Station (ISS) which is essentially a spacecraft suspended in space. But on the other hand the conditions on Moon are pretty hostile, so techniques to survive and sustain research labs on Moon can help us in a longer run to learn how to handle some of the challenges we face while moving into deep space.

The astronauts from Apollo missions brought back samples of rock which showed some traces of water, however it was considered to be contamination from Earth as the containers in which they were brought had leaked and considering the bone dry nature of rocks from Moon they would have a greater affinity to absorb moisture from atmosphere.

NASA’s Cassini spacecraft which passed by Moon in 1999 on it’s way to Saturn provided signals showing detection of water/hydroxyl. The Cassini data shows a global distribution of water signal with the stronger signals received from the poles.

The Deep Impact spacecraft, as part of its extended EPOXI mission and at the request of the M3 team, made infrared detections of water and hydroxyl as part of a calibration exercise during several close approaches of the Earth-Moon system en route to its planned flyby of comet 103P/Hartley 2 in November 2010.

The signals from three different instruments on board Chandrayaan-1, Cassini and Deep Impact Spacecraft answers questions that scientists have been long looking for.

Ever since the “push” became the buzz word for iPhone 3.0 OS, I was curious to find out how the push notifications worked with iPhone. My initial thought was that, iPhone needed a dedicated push server visible within the operator network, just like Blackberry, but then how did iTouch used the same apps and still used the push notifications for the Wi-Fi. I began investigating and found a cool technique that Apple implemented for it’s push notifications, but I also found out a few things that I really didn’t like.

Why Push?

There is an inherent problem with the iPhone OS and the problem is that there is no “backgrounding” on iPhone, which means unlike other smart phones, the apps don’t run in background on iPhone when you exit them. This effected applications for iPhone which needed constant polling with a publication server. E.g. a RSS reader application won’t be able to poll the feeds for the new updates from the phone. To read the feeds, the user will have to open the application and manually fetch the feeds. To address the issue Apple came up with a smarter approach. They implemented push mechanism for iPhone.

Poll vs Push

An application constantly running in the background of your phone and polling for feeds or updates causes battery consumption. So if you have multiple applications doing the polling from your mobile device, your battery might get drained pretty quickly than you expect. Push however doesn’t implement the poll mechanism and you get updates as it happens.

So how does the “push” work in iPhone?

Okay, consider this, you have an application on iPhone which enables to have the push mail experience for your Gmail or AOL or any of your home grown IMAP email server. Here is a representation of how “push” mechanism would work with iPhone.

 

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Apple implements an intermediate server (under their own control and not under operators control or visibility) called as the Push Notification Server (PNS). The device (iPhone) maintains a constant TCP/IP connection with this server. The application developers server (or the 3rd Party Server) maintains a session with the mail server. When a new mail arrives an alert will be sent from the application developer’s server to the PNS which then pushes it to the iPhone 3.0 through the open TCP/IP socket connection. So if you had a RSS reader application, to have notifications sent to you automatically as update on a feed is available, the application developer will need to constantly monitor the feeds and notify the PNS as anything happens.

Essentially what Apple has done is moved the polling or processing need from iPhone to an intermediate level called the “App Developers Server”.

Sure this approach works for the battery benefits where background applications can claim as much as 80% of battery drain as compared to 20% on Push notifications using Apple’s technique. However the way I see it, there are some issues.

So what are the issues?

The first issue that I see from an application developer stand point is that, if I had to write a RSS reader type of application then I would have to deploy my own backend server which would monitor the feeds for the end users and notify PNS to have notifications on updates. Basically not all applications really need a backend service, but with this technique that additional layer has to be implemented. So if the number of users for my applications grow, I’ll need to setup a server farm and to recover the cost I’ll need to increase the cost of my application or charge the user a service fee which is not good either for me nor for the user.

The second and most concerning issue that bothers me is, privacy issue. Well if a third party application developer needed to constantly monitor your inbox or IM or even the RSS feeds, then it would need your credentials to establish and maintain a session with the actual mail server/chat server or should know exact feed URLs so that it can monitor them incase of RSS. How many people would really feel comfortable to know that their email usernames and passwords are being stored on a 3rd party server probably unencrypted and probably anyone managing the server would have visibility to it? To me this is the biggest issue with this approach.