Category Archives: Astronomy

Just finished “The Martian” book

What a terrific read! I know, where have I been… I haven’t even seen the movie; my friend Charles loaned me the book last week and I read it today. All the way from Sol 6 to Sol 549. Weir hit it out of the park!
Loads of fun, well done from a general science-y point of view, and gave a generally fair picture of aspects of NASA that were coherent with this old JPLer’s memory. NASA has its extreme bureaucracy, but when the scientists, mission designers, engineers and marvelous machinists (gotta have those marvelous machinists) got running on a project, the enthusiasm and expertise was awesome.
In 1990, I switched over from Division 33, Section 333 Communications Ground Systems, to Section 336, Spacecraft Telecommunications Equipment, to help build Earth-orbiting radars and, later, transponders (two-way data radios) for Mars-, Jupiter-, and Saturn-bound missions. Ultimately I got to lead a group within 336, Spacecraft Transponders; we had a tremendous assortment of projects going on in the group of about 25 to 30 engineers, scientists and technicians.
While reading the book today, I had to trace the character Mark Watney’s sojourn across Mars to get and keep my bearings. Fortunately, someone at JPL had already taken care of that and I was able to scope the important spots out by using the Mars Trek app in my browser!

Iridium 47 spotted

I have a nifty little app called iFlare, and it reminds me of Iridium flares. Tonight I got the opportunity to see the -4 magnitude flare from Iridium 47!

With a waxing moon high in the south, it was a little hard to get good dark adaption. However, I was barely able to see +4 stars in the area (like the parallelogram of Lyra). The location for the maximum was a few degrees SE of Vega, and about 10 seconds before the maximum I caught the satellite N of Vega and headed toward the SE.

After the maximum, it was possible to follow the satellite for about 20 degrees, fading out before it got as far as Rasalhague. That 20 degrees was about 30 seconds or so, I think.

The Deep Space Network

In 1985 I had the opportunity to travel around the world for the NASA Deep Space Network (DSN). Left LA the last day of June, didn’t return home until mid-September. Along the way got to see some neat things, including the Southern Cross, the Magellanic Clouds, the lack of a southern polar star, kangaroos, more cockatoos than I’ll ever need, and the other two Deep Space Stations, DSS-40 (Tidbinbilla, Australian National Territory) and DSS-60 (Robledo de Chavela, Spain).

DSN_Robledo_Aug1985

In the above picture of the site at Tidbinbilla, the 64 m dish is center right, while the 34 m HA-DEC (hour angle / declination) dish is to the left. The 64 m dish was subsequently embiggened to 70 m. The HA-DEC antenna is long gone. This JPL site discusses the advantages and disadvantages of the HA-DEC.

My trip was to lead the installation and test of the Base Band Array (BBA), two “NASA-blue” 7′ high rack-fulls of a state-of-the-art signal-processing system that would allow the real-time combining of received radio signals from each antenna at a site, and provide nearly the full signal gain that was possible. The BBA digitized the baseband signal from each antenna, then ran it through a correlator, and summed together the signals.  Given that each DSS had a 64 m, 34 m, and at least one 26 m dish, it was possible to get nearly 1.6 dB gain over the 64 m dish alone. I think we were able to achieve better than 1.5 dB.

Why go to all that trouble for a measly 1.5 dB? Voyager 2 was on the extended grand tour phase of its trip, and emerald Uranus was coming up in 1986. That extra gain meant more images and science data coming back from Uranus!

More on the Deep Space Network is available here, including a little narration from my former section manager, Dr Al Bhanji!

Canopus on my cheap webcam!

Here in Phoenix we’re fortunate enough to get a glimpse of Canopus every winter at it rises a few degrees above the southern horizon. Tonight, I pointed the $65 webcam atop the roof at the saddle between Camelback Mtn and Mummy Mtn, and waited for Canopus to ease into place.

Canopus_28Feb16_212000_n7uv2

There’s some thin haze and wispy clouds tonight but not too much. The neighbor’s porch lights are at the bottom of the image, and the ghostly rise of the palm trees across the street are visible in silhouette. From the camera, the bearing to Canopus is about 189.8° az by 2.8° elevation, a line that crosses over the east end of the runways at Sky Harbor and also over a lot of city lights.

Not bad for a $65 camera.

 

Are the Moon landings becoming only a myth?

Astronaut Ed Mitchell’s death is a great loss.  He is a true hero, one of the many who worked so very hard, who risked so much, with such diligence and camaraderie, to get us to the Moon. I wonder what happens as those, who did these amazing things, and lived those times, are “succeeded” by those who are technologically ignorant. What happens when those who prefer to believe that the Moon is painted on a celestial sphere and spun by a mythological entity gain political power and control?

As someone who had a very small part in unmanned space flight, but who got to experience some of the tremendous rushes of success and heartfelt loss, I hope that somehow this country pulls its collective head out of its nether regions and focuses on science and exploration, not bombing others back to stone.

Freezing water when it’s not freezing outside

Ok, it took forever to get the blog running again, but today I’m playing with temperature and the dark sky. I don’t have a lick of math to back anything up (yet), but here’s what I’m seeing.

I have a cheap weather station (from Costco) .Img_3736_small

This wx station comes with an “outdoor” temperature sensor.

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I also have a near dead-flat white foamed roof on the house (seen in the background of the sensor above). I remember a long time ago one of my great mentors Bart telling me about the ability to use the cold of deep space to freeze water outside even when the air temperature is above freezing.

I’m here in the desert, and it’s fairly dry atmosphere. The ambient air temperature (as measured by the Davis wx station about 8 m away and 2 m higher)

Img_3741_small

is 47F (281K) right now, and the sensor sitting on the roof is showing 27.3F (270K). So 11K colder. Early this morning, when the outside air temp was 272K, the roof top sensor was showing about 264K. Hard freeze temperature. If I put a pan of water on the roof next to the sensor, it will be a disc of ice in the morning. Pretty neat!

So, how’s this work? I suspect that the hemisphere of sky that the sensor is exposed to above is pretty cold, significantly more than the 3K of the CMB but not anywhere near ambient air temperature. There’s a few palm trees that stick up into that hemisphere, but that’s a small portion of the overall scene, and palm trees probably don’t have a lot of heat contribution, though they do reflect the ground, which is currently over 273K. Since the atmosphere is fairly empty, there’s not a lot of heat energy between the roof and space – it’s a clear night. That lack of heat means that there’s probably not a lot of energy to illuminate my temperature sensor laying flat on the roof. So, for that hemisphere (at least), the heat energy available is pretty low.

Now on to the other hemisphere, the one below the sensor laying flat on the roof. Well, it’s all white foam and provides a pretty good insulation from the heat of the house and the ground and shrubberies, etc., nearby. The foam under the white coating is a closed cell yellow foam and probably has pretty poor heat conduction. Given that the foam also is low density, it probably doesn’t have much heat capacity so there’s not much contribution of heat energy from that lower hemisphere, and I imagine it cools rather quickly once the sun goes down.

So, here I’m measuring the temperature at the air layer about 1 cm above the roof, and well below the parapet wall around the roof at about 20 cm. It’s dead still tonight, so there’s little air mixing at the roof level. The Davis wx station uses their usual baffled temperature sensor and is pretty close to the other temperatures measured locally, though I suspect it’s biased a bit by being so close to the roof, and not on a nice piece of open land as per NOAA/NWS siting guidelines.  I’ve got a homeowners’ association to deal with, doncha know…

Anyway, I will try to get some calculations going and see what I should be able to see. If I get very ambitious, I might even build a temperature sensor “tower” that can measure the temperature at a number of distances off the roof (from touching the roof to maybe 100 cm) and see what the gradient looks like.

This also explains why the truck windshield gets frost on it some night but not others. The windshield will chill due to seeing mostly the cold sky, and it will chill faster than the ambient air when there’s little air movement. If the temperature on the surface of the windshield gets below the dew point, then I should see water ice plate out on the windshield. This happened a few nights ago, and the ice was pretty resistant to defrosting.

 

Venus and Mercury

After a number of days of clouds and rain here, I walked out of the grocery store and was impressed to see two bright planets low in the western sky. One was obviously Venus, the other was a little orangey and initially I thought it might be Mars. However, a quick check on the Internet shows it to be Mercury!

Both planets stand out beautifully in the twilight sky, and with Mercury preceding its brighter sibling toward the western horizon. I pointed the N7UVCAM2 Roving Reporter toward the pair, and captured a few images. I will post them here as soon as I figure out what’s going on with WordPress.

What Good Is a Wireless IP Camera?

I recently installed a new weather station here at the homestead. With a weather station, it’s always nice to be able to have a picture of the sky to see what the sky looks like, to augment and bring to life the sparse yet functional gauges and dials.

The world of digital image capturing devices is a miasma of terminology, mis-terminology, ignorance and sometimes (at least so it seems) a bit of disingenousity. Go to eBay, type in “IP network camera outdoor”, and there’s at least a zillion, give or take, cameras available from no end of sources, mostly in Asia.

Not being really up on the latest and greatest for IP network cameras, all I really knew going in was what I wanted. The camera needed to be 1) able to withstand living outdoors, in the direct sun and rain; 2) at least 1080p vertical resolution; 3) as sensitive as practical, so I could see an image at night, and hopefully see a few stars; 4) cheap (hard to define); 5) have an included webserver so that with a browser it’d be possible to see the image, and be able to ftp an image on a scheduled (not event) basis to the WUnderground site where my Personal Weather Station data is displayed; and 6) straightforward to configure and tweak. I know, it’s a lot to ask, especially with 4).

One thing that is missing in the above list, and some might wonder why, is the choice of wired vs wireless for the connectivity. After all, it’s the “WirelessJon” website! For this particular installation, it really wasn’t much of a decision to make. A camera takes a significant amount of power to operate (several watts at least). A wireless camera takes at least as much power to operate as an equivalent wired camera. Since a wireless camera would need a source of power, likely the house mains, a cable would still have to be run to supply the power to the camera. If I’m going to the trouble to run wire, I might as well kill two birds with one stone and use that wire to supply connectivity as well. Also, my desired camera might be streaming video on occasion, and that could end up being a significant load on my home wireless network. Finally, ensuring that the wireless coverage from the inside of the house would be good enough for robust connectivity to gadgets on the roof would mean that there’d be a constant unknown as to whether or not a problem in viewing the camera’s image was caused by RF propagation or by some hardware issue. So, like I said, the decision to go wired was pretty straightforward. I have another reason which made it simpler to go this way, which I’ll discuss in a future post on rooftop routers.

As can be imagined, many of the requirements listed above are mutually incompatible. And by “cheap”, I was aiming for somethiing under $100 delivered. Nonetheless, I started my search through Google and eBay as well, working to figure out some of the more esoteric terms (RTSP, DNC, AE, etc.) and attempting to validate things like FTP server and web browser functionality and configurability. A simple thing that I wanted was a scheduled capture on a regular, timed basis – something that doesn’t seem to be offered in most cameras listed on eBay – most offered appear to target the surveillance video market, and the cameras trigger video based upon events like movement in the field of view, or whatever. There were some challenges to figure out what many of the cameras actually did.

Another minor tricky thing was camera sensitivity to light; remember in my wish list I wanted a camera that could even see stars (not just the Sun). I’ve always had in my mind something that I call the PoleCam, which is a camera trained at the north celestial pole and capable of watching the current pole star, Polaris, in its daily orbit around the north pole, Yep, it’s true, Polaris isn’t really at the celestial pole. It’s close (about 3/4 of a degree away, close enough for government work), but it’s not stationary. The ideal camera would allow me to see the movement of Polaris as well. But, I digress: the main purpose of this camera is weather observation.

Cameras come with two different types of image sensor, CCD or CMOS, and a variety of lenses with different angular fields of view (FOV). Some cameras have varifocal lenses, where the “zoom” factor of the image can be changed to accommodate. For me, CCD is the only way to go for improving low-light sensitivity; compare a CCD imager with its equivalent CMOS imager and you’re sure to find that the CCD imager provides a higher quality image with better low-light performance. As far as lenses, it seemed that there were generally 4 mm, 8, mm and 12 mm used on the cameras for sale. Since I’d never bought one of these cameras before, I didn’t know how difficult it’d be to change the lens, so I decided to go with an 8 mm lens which should have about a 40 degree horizontal FOV.

A tricky thing I discovered (I know, I was born yesterday) was that some of the eBay ads had confusing, conflicting, or flat incorrect information about the product offered. Doing searches which included “CCD” didn’t always return only cameras with CCD imagers – in fact, some sites would use the term “CCD” in several places when selling a CMOS camera. Also, attempting to figure out if a camera had a webserver built-in, and whether that webserver could respond successfully to queries that came in on Chrome, or Firefox, or whatever, not just IE, is quite challenging.

Suffice to say, I did find a camera which appeared, at least in theory, to meet many (but not all) of my desirements. The camera I discovered appeared to have the following features: 1) outdoor operation, with an included sunshade; 2) 1920 x 1080 resolution; 3) CCD imager for good low-light sensitivity (hard to tell until it’s in your hands, though); 4) $70 delivered; and 5) built-in webserver, FTP server, etc. The things it didn’t appear to have included: 1) power over Ethernet (PoE), so I’d have to do that externally; 2) no idea of what the software was or how to configure the camera for my desired operating method; no idea if the camera was any good at all given the low price, and many other unknowns which wouldn’t be answered until I had one in my hands.

So, I placed the order on eBay and awaited delivery of my amazing new $70 super webcam. More soon on what I found out when I opened the box!