CrowdSat

The third CrowdSat question comes from SEDSAT-2 Communications team leader Lavina, from Philippines SEDS. Finally, we have a question that is both out of my domain (I am not an electrical engineer) and is not easily Googled...

We are considering using a 2.4 GHz frequency (either with a dipole or a grid oscillator antenna) as opposed to the 420 MHz we had initially thought of. The trouble with the higher frequency, accoridng to our advisor, is that it would contribute to a higher free space loss. We were wondering if there was any way to offset this loss? And if there's anything else we should consider with regard to the 2.4Ghz vs Mhz question?

Not a problem! This is what the CrowdSat idea was really designed to do: bring in people that have real experience and knowledge to answer your questions. Looks like I have to stop faking it sooner than I thought and get some help...

Help comes from a friend of mine from University of Illinois who now works at Northrop Grumman. Chris says:

Off the top of my head cubesats usually use the 100s of MHz band because it makes transmitter design and receiver design simple.  The parts in that band are cheaper and there will be less interference generated and received by the comm electronics (filtering is easier at lower frequencies).  At 2.4GHz, there will be high atmospheric absorption (especially if theres moisture in the air).  This will require better coding schemes or more transmit power or both.  Simply put, its more cost effective, design is easier, and less power is required with comm in the MHz rather than in the GHz.  Try searching under atmospheric absorption to pull a graphic like this: http://www.everythingweather.com/atmospheric-radiation/absorption.shtml. As the wavelengths get into the GHz range, absortion goes way up, and transmission goes way down.  They may ask why commercial/government satellites use GHz communications.  Its more secure, there's more bandwidth available, and they aren't as power limited as a tiny cubesat.

The second question comes from Heriberto from the SEDS chapter at Instituto Tecnologico y de Estudios Superiores de Monterrey (ITESM) in Mexico. Apparently he and his friends are starting a CubeSat program at his university -- great to hear.

Question 2: Can we choose our working orbit or do we have to follow an established orbit?

Since there are so few CubeSat launches available each year -- if there even is a launch available in a given year -- you are likely stuck with any orbit that you can get. CubeSats are launched as secondary payloads, meaning that they are placed in a similar orbit to the primary payload; this is how the launch cost for a CubeSat can be so "inexpensive" (if you can call ~$50,000 inexpensive, but you take what you can get).

Looking at the CubeSat Community Website, there have been six CubeSat launches:

1. 30 June 2003. Six CubeSats were launched aboard a Rockot rocket from Russia. The primary payload was the Canadian Space Agency's Microvariability and Oscillations of STars (MOST). The CubeSats were placed in a circular sunsynchronous orbit with an altitude of 820 km.
   
2. 27 October 2005. Three CubeSats were launched aboard a Kosmos-3M rocket from Russia. The primary payload was SSETI Express. The CubeSats were placed in a 686 km circular orbit at an inclination of 98 degrees.
   
3. 21 February 2006. One CubeSat was launched aboard an M-V-8 rocket from Japan. The primary payload was JAXA's ASTRO-F satellite. The CubeSat was placed in a sunsynchronous polar orbit with an apogee of 751 km and a perigee of 290 km at an inclination of 98 degrees.
   
4. 26 July 2006. Fourteen CubeSats were launched aboard a Dnepr rocket from Kazakhstan. However, the rocket failed to reach orbit. The intended orbit was a 500-600 km circular sunsychronous orbit at an inclination of 97.43 degrees.
   
5. 11 December 2006. One CubeSat was launched aboard a Minotaur rocket from the United States. The primary payload was TacSat-2. The CubeSat was placed in a circular orbit with an altitude of 410 km and an inclination of 40 degrees.
   
6. 17 April 2007. Seven CubeSats were launched aboard a Dnepr rocket from Kazakhstan. The primary payload was EgyptSat 1. The CubeSats were placed in an approximately circular 700 km orbit at an inclination of 98 degrees.

That's the basic information from the CubeSat launch history. Launches for a CubeSat are quite rare, so if you do find a rocket that is willing to host your satellite, go for it. If you wait for a perfect orbit, you may be waiting for a long time.

Does this information help?

(ps: I'll post sources and more precise orbital parameters as I find them...)

I have a number of student friends in India and a few other parts of the world that want to build a small satellite. That's how this CrowdSat idea got started.

First, I've been advising the SEDSAT-2 guys and girls as they attempt to design a satellite. The problem for me, as a systems engineer in my "real" life, is to understand the connections between the SEDSAT-2 members, who range from the Philippines to the UK to the US and a number of places in between. How do they communicate? How do they share their information? How do they get from point A to point B in their design? (How do they know where point B is when they are at point A?)

I'm no expert. I'm 26, and on 30 October -- coincidentally, my dad's birthday -- I'll complete my one year anniversary as a systems engineer at Orbital Sciences Corporation. CrowdSat is how I am going to get expert advice for these students and, by teaching them the fundamentals of small satellite design, learn about many of the points myself.

Anyway... that's the background. Looking forward, I think I'll keep this project as simple as possible. Students will have questions. I will find answers, and when possible, I will find people with a lot more experience than me to give the answers; let's be objective, I don't know all that much more than the students.

 

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Question 1: What exactly do I need to have in a CubeSat proposal?

The first question comes from Amrut, a graduate student at Christ College in Bangalore. Amrut invited me to make a presentation to his physics classmates at Christ College when I was in India in September. He also was one of the organizers of the Astronautical Society of India's Student Chapter. What does he want to do with his ASI friends? You probably guessed it: build a satellite.

My advice: approach this like a business plan. Who will your investors be? What is your market? What resources will you need? What staff do you need? What is your timeline? What is your objective?

I'll address a few of these in brief, but I will chiefly rely on questions to advance the point.

1) The most important question to ask yourself: why? What is your objective? What makes your project unique enough for someone to invest their time or money in it? For a university, it might be enough to say "this is the first satellite that has ever been built by our university" or "this will be the first CubeSat launched by India." At the university level, CubeSats = education. But, in my limited experience in working with Indians, you should also pursue a practical purpose and bring some real benefits back from your mission.

2) What is your product? It's not just the satellite that is your product -- it's the data you receive and how you use it. It's also, I think, how your team is seen by the "outside world," that is, how you market your efforts. For your university and for your future employment in the industry, it is also important to consider that the knowledge and experience you gain is also a product that you are developing, because you will be better satellite scientists and engineers if you have experience.

3) What is your strategy to complete the mission? Consider your timeline -- recruiting a team, designing and reviewing, testing and integrating, searching for a launch provider, searching for sponsors. It all takes time. How will you get from point A (nothing) to point B (your satellite in orbit, sending data to Earth)?

4) What resources will you need to complete your mission? Of course, the first thing in your mind will be money. It's a valid point, but let's save it for later. Also consider that you should have experienced technical mentors. You will need tools for building and labs for testing. You will need materials. Sometimes you will need to travel. Most important: you will need a launch vehicle! Know what you need so that you can go and get it.

5) What staff will you need? For the most part, this will be your scientists and engineers, your fellow students. But consider also that you will need people to develop and operate the ground stations, people to crunch the data, people to get the money and publicity. It is like running a company in some regards.

6) What finances will you need? Launching a satellite is very expensive, much more expensive than actually building it. Consider how much you need. Consider also -- and this is very important -- that as a student, it is often possible for you to get in-kind donations, that is, to get donations of materials or lab time or other goods and services that you would otherwise spend money for. Not spending money for something is a great thing.

 

I think of this part of your project -- the proposal -- as the business end of your satellite. The engineering side will have its own unique approach, turning your objective into a series of methods to achieve it, then understanding the driving systems requirements, then trading your different approaches to find the best approach, etc. So what I tried to do here is take my best guess at how you should get started. I will try to get some more experienced people here soon to help. Remember: I am no expert.

What do you think?