Frequently Asked Questions
Your project mentions iPhone and Android apps, as well sponsorships being open "to anyone with a smartphone." So, what's a Windows user without a smartphone to do?
If you have a web browser, you'll also be able to request pictures and send/recieve messages. We will be creating a web UI to our server back-end. The ArduSat folks whom we are working with have similar needs, so there will definitely be some way to get communication to/from the satellite with just a browser.Last updated:
NASA's CubeSat standard contains a specific ban on pressure vessels of any kind. How are you planning to get your CO2 cartridge on board to inflate your balloon? Are you getting a waiver for this?
SpaceX - our launch provider - is not part of NASA. We have reviewed this with Spaceflight Services; here is their answer, verbatim:
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You are correct that you are not required to comply with the Cubesat standard; your gas cartridge is not disqualifying—nor likely an issue unless implemented in a dangerous manner, which I doubt.
The procedure is that the cartridge—along with anything else considered "hazardous"—must be identified in the Payload Questionnaire (PQ) and later in the Missile System Pre-launch Safety Package (MSPSP). E.g. PQ item #13: “Description of any pressure vessels to be used on the spacecraft.”
These documents define what hazards need to be disclosed and are used by Spaceflight, and then SpaceX and the range, to formally assess if the risk is acceptable. (This sounds onerous, but know that folks tend to be worried about things like big tanks of hydrazine and ordnance, not CO2 cartridges; these documents are how you tell everyone officially you don't have a hydrazine tank.)Last updated:
Will the pictures only be of the Earth? Could I request a picture of the ISS or the moon? A picture of an astronaut working outside would be very cool.
You could *try* to get a picture of the ISS/Moon, but probably would not be very successful. Here are the problems:
1) The cameras are going to be fairly wide-angle, with at least a 60 degree FOV. At that size, the Moon would be very small - only a few pixels across.
2) Our orbit does not take us any closer than several hundred km (at best) to the ISS, and our relative speeds would be many thousands of km per hour. So even if you got the ISS (and an astronaut) in the FOV, they would be a tiny dot, whizzing through at many pixels per second.
It's a very cool concept, though.Last updated:
What's the image resolution of the camera? Can you request specific images by time and location? (e.g. an image pacific ocean at sunrise)?
The maximum camera resolution is 640x480, i.e. VGA. That's less than what people are accustomed to these days, but we're really limited by bandwidth: we can only transmit images down to Earth during the brief (~5 minute) intervals when SkyCube is passing over one of our ground stations. And the radio on board gives us at best a data rate of 57.6 Kbps. That's not exactly broadband internet speeds, but it is certainly much faster the 9600 baud typical of most CubeSat radios. We figured it would be better to radio a selection of multiple VGA-res images down on each pass, rather than a piece of a single HD image.
You will definitely be able to request an image at a specific time. Location is a bit trickier, since it depends on the time. We have no control over where the satellite will be at any one time - Sir Isaac Newton is doing the driving! But since we will know its orbit, we can calculate the time when it will be over a particular location. In fact we're planning to build that ability into our smartphone app. So you'll be able to ask, for example, "When will SkyCube be over Afganistan?" and request a picture at that time.Last updated:
Yes, but only VERY SMALL Borg.Last updated:
Do you have any more details about the "inexpensive amateur radio equipment" that will be required to receive the data bursts form the satellite directly?
One member of our team has already been able to detect beaconing from M-Cubed (another CubeSat already in orbit), using a handheld Yaesu FT-60R transceiver with nothing more than the built-in antenna. That's the bare minimum equipment you'd need to detect pings from SkyCube (the FT-60R can receive up to 999 MHz, and we broadcast at 915 MHz.) Note that we say *detect* but not *decode* - to actually decode the "tweets", you'd need to increase your signal-to-noise ratio with a larger antenna and RF preamp (such as our ground stations will have.)
But in the absence of such equipment, you could add a cheap Yagi antenna to greatly increase sensitivity. Data on our every-10-seconds beaconing pings will be modulated at 9600 bps; our team member is working on an iOS app which may be able to use the iPhone's built-in audio hardware to demodulate the data and decode the messages directly. While we think it will work, we have not actually proven it yet! Nevertheless, here's an example of what amateurs can do with the kind of equipment mentioned above:
How are you going to be able to control tumble & spin? How will the camera be aimed at the earth, and maintain its directionality?
That is a great question. SkyCube will have passive magnetic stabilizers which will keep it aligned to the Earth's magnetic field. This is a time-proven technique for orienting very small satellites. We are solving the other problem by putting multiple cameras on board, so that at any one time, at least two cameras will be pointing Earthward. The satellite's software will be smart enough to throw away images that contain black (empty) space.
We've given some thought to making SkyCube an actively-stabilized satellite, but it's difficult to do in a 1U frame, given that half of our volume is occupied by the balloon. If we surpass our fundraising goals, we may be able to make SkyCube a 2U and add capabilities like active stabilization.Last updated:
Why is SkyCube using 915 MHz for broadcasting from space? Most other CubeSat projects use 437 Mhz. 915 MHz is an unlicensed band in the USA so lots of people use it. These other users can make it difficult to hear the 915 MHz signal from the satellite.
What mainly drove us toward 915 Mhz for the current mission is the fact that we can take advantage of the high-bandwidth US Navy/Boeing/Utah state ground stations. For an application where images are a prime product, bandwidth is everything. And even tho we're operating in a noisy part of the spectrum, the data rates those stations are capable of are an order of magnitude higher than anything we could have done (within our budget) in the 437 MHz HAM bands.
Off-the-shelf CubeSat radios using 437 MHz currently offer a maximum of 9600 bits per second on the downlink. What we're promised by using these 915 Mhz MC3 ground stations is 57.6 kbps minimum, and sometimes up to 115.2 kbps. That seemed like a fair tradeoff for switching from 437 to 915 Mhz. And our radio is something like 1/3 the cost, since it's a clone of the one already designed en masse for Boeing.Last updated:
But 915 MHz is only an unlicensed frequency in the United States. Would SkyCube have to be switched off over the rest of the world?
Actually, 915 MHz is an ISM (Industrial-Scientific-Medical) band across all of ITU region 2. That includes North and South America, Hawaii, and a good bit of the Atlantic and Pacific oceans. Certain other countries outside Region 2 (Australia, New Zealand, Israel, and a few others) also permit unlicensed broadcasting on 915 MHz.
In most of Europe, there is an unlicensed ISM band at 868 MHz. This band currently used for things like Zigbee (Z-wave) transmitters and radio modems. 868 MHz is just within the broadcast frequency range of our current radio hardware, so we may be able to broadcast at 868 MHz while over Europe. We're still researching the regulatory issues there, however.
The bottom line is that we will run SkyCube in accordance with all local telecommunication regulations. SkyCube will broadcast everywhere, except where prohibited by law.Last updated:
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