工程师故事：打造一颗业余卫星(5)

先前我们已经介绍很多有关打造ARISSat-1计划的基本资料了。这项计划一开始的想法是要在宇航服中填满电子元件，然后再将它从国际太空站(ISS)上发射出来。经过一波三折，我们后来却失去了宇航服及设备。但真金不怕火炼，更何况我们还有铝制太空框架。最后终于看到了圆满结局──我们打造的ARISSat-1成功发射了！而且也顺利地在太空中运行！

无论是大型或小型的计划，设计者们都面对着未知的挑战。我们究竟遇到什么样的问题？我们又是如何找到解决方案呢？藉由开发团队中的一些小故事，让我们一起来探索这项计划的一些设计挑战、架构及其解决方案。

ARISSat-1计划从一开始的构思、设计到制作完全都来自一群自愿参加的人员。我们一开始只有一个简单的概念，接着就到处呼朋引伴邀请具有特殊专长的人才加入。因此，随着该计划的范围扩大，这个开发团队的规模也与日俱增。有句话说得好──“如果想要好好完成事情，就交给忙碌的人去做吧！”(If you want to get something done, ask a busy person to do it.～Lucille Ball)

Sergey Samburov (RV3DR)首先提出他的想法，但总计超过50人致力于打造这项ARISSat-1 计划。几乎所有的自愿参与人员都在工作或兴趣上专精于某种方面的技术：电子、机械、科学家、技术人员、IT人员、程序设计人员和教育工作者。对Phil Karn (KA9Q)来说，我们在白天其实并没有充份的时间来进行这项计划。但我认为，白天我尽力完成客户的需求，晚上就可以做一些想学习的新东西。

初期SuitSat-2 卫星控制台/无线电/天线概念原型。由左而右的宇航员分别是Alexander Kaleri、Mark Steiner (K3MS)与Sergey Samburov (RV3DR)

我很确定开发团队的其它成员们也认同我的看法──这项计划的“报酬是你得以做一些很酷的工作！”在从1到10的量尺上，这项计划的得分是11 。不过，这可不是什么轻松的事，而是个艰苦的工作。ARISS 硬件经理Lou McFadin (W5DID)回忆道，“自愿参加者在计划开始之初总是怀抱着极大的热情。但随着时间进展，也逐渐失去兴趣或者还有其他任务要做。”

ARISSat-1计划的振动试验。从左至右分别是Lou McFadin (W5DID)和Gould Smith (WA4SXM)

因此，自愿参与的人员们来来去去。一个如此庞大而复杂的计划随时可能让人失去兴趣与热情。这项计划将以其步调持续前进，大家也都有自己的生活与家庭。然而，对于那些坚持这一计划到最后的人，它也为其带来了十分令人满意的体验。诚如AMSAT 工程副总裁Tony Monteiro (AA2TX)所说的，这是一个关于开发团队间情谊的美好故事：

“软件定义转发器( SDX )首先在2009年4月4日完成。开发工作已经持续了好几个月了，整个团队第一次全部聚集在Microchip公司共同整合硬体和软件。经过连续几天精神紧绷地工作后，大家都开始感到有些精神不济。我们当时正专心致力于取得摩斯电码 (Morse Code)讯号的工作，它是第一个由SDX产生的讯号。最后当它终于发出绝对完美的摩斯电码时，大家都兴奋地相互击掌并且开怀大笑。一直到Lou指出从SDX传来的完美讯号一点儿也不像真的摩斯电码的声音时，我二话不说，赶快在软件中加入几行指令，再重新载入SDX 。当SDX再度执行时，摩斯讯号灯发出像二次世界大战时旧式AN/ARC-5真空管发射机的唧唧声，几个大男人放声大笑，那种就像一群淘气孩子们般嬉闹的热闹场景，这些都是令人永远忘不了的回忆。”

经历了多次修改后，硬件总算正常运作。三至五次的修改已经是家常便饭。我们从这一原型设计中看到了还有许多值得借鉴之处──特别是从硬件搭配检查与互连。Jerry Zdenek的家用录影机逻辑：

“让所有的逻辑栅都能整合于CPLD是一项挑战。视频撷取经由简单的SPI介面传送到平行主机埠，然后也为其添加影像资料分析。偶尔，它会没来由地停止搭配。我花费了好一番功夫后，最终总算将电路板建构在一个更大、更新的CPLD上，以实现一个更弹性化的架构。”

每个子系统都有一个微控制器以及许多编程──包括繁复的序列通讯链路。Jerry说明如何将所有的程式码整合于电源供应器( PSU )上的8位元微控制器PIC16F887内部：

“我必须一直反覆、添加和移除程式码与资料，并为其进行最佳化，直到它顺利执行。除错工作也变很有趣，因为即时I 2 C正与执行于另一处理器上的IHU通讯。而在PSU上没有除错序列埠。所以，在I 2 C启动且能可靠运作以便传送除错资料以前，我都得使用两台电脑并分别利用每一处理器来逐一步骤进行。USB逻辑分析仪在最糟糕的情况下也可能发生中断或遗失数据串流的情形。太有趣了！”

这一计划的开销由谁来买单呢？自愿参加者贡献了自己的时间、也提供了工作平台以及测试设备。但还有一些必须要购买的材料以及旅行安排，如机票和酒店，以便使大家能在周末与NASA召开工作会议以及进行安全性估。答案是大多的经费都来自于AMSAT。AMSAT是一个非营利性的业余卫星研发组织，其营运与经费来源主要依赖会员年费以及各界捐款。

多次周末工作会议的一张团体照。由左而右分别是Bob Davis (KF4KSS)、Jim Johns (KA0IQT)、Tim Moffat、Joe Julicher (N9WXU)、Larry Brown (W7LB)、Phil Karn (KA9Q)、Steve Bible (N7HPR)、Bill Reed (NX5R) 、Jerry Zdenek (N9YTK)、Lou McFadin (W5DID)以及Tony Monteiro (AA2TX)。

现在你了解这项计划的挑战、策略及其解决方案了。这绝对不是一个故事而已，而是所有开发团队人员付出时间与心血的艰辛工作。而我们得到了什么回报呢？它让我们有机会从事这样一项超酷的开发计划，并与一群了不起的工程师们共事、学习新事物以及结识新朋友。但最重要的看到并且听到来自世界各地使用ARISSat-1业余卫星的人们的喜悦。

本故事系列文章：

工程师故事：打造一颗业余卫星(1)

工程师故事：打造一颗业余卫星(2)

工程师故事：打造一颗业余卫星(3)

工程师故事：打造一颗业余卫星(4)

工程师故事：打造一颗业余卫星(5)

点击参考原文：Chips in Space: Design challenges, intrigue and solutions

《电子工程专辑》网站版权所有，谢绝转载

{pagination}

Chips in Space: Design challenges, intrigue and solutions

Steve Bible

We’ve covered a lot of ground in the past seven blog posts. The story had a beginning of an idea (hey, let’s fill a suit with electronics and toss it out of the International Space Station!). Twists and turns (we lost the suit, now what?!). Heroic recovery (that’s a nice aluminum space frame you got there!). And a happy ending (We have liftoff! ARISSat-1 is successfully operating in space!).

With every project large or small, there are challenges the designers face—the unknown. What problems did we encounter, and how did we find solutions? Let’s explore in this blog post some stories of design challenges, intrigue and solutions.

ARISSat-1 was conceived, designed and produced entirely by volunteers. We started with an idea and we called upon people with the necessary talents. Thus, the team grew over time as the project scope widened. There is so much truth to the statement, “If you want to get something done, ask a busy person to do it.” – Lucille Ball.

Sergey Samburov (RV3DR) had the idea, but more than 50 people worked on ARISSat-1. You could say that almost all of the volunteers are technical in some fashion, at work and play: electrical, mechanical, scientists, technicians, information technologists, programmers, and educators. In the words of Phil Karn (KA9Q), we don’t get enough during the day. I like to say that during the day I do what the customer needs me to do, and during the night I do something new I would like to learn.

Early SuitSat-2 Control Panel/Radio/Antenna Concept (from left to right Cosmonaut Alexander Kaleri, Mark Steiner (K3MS) and Sergey Samburov (RV3DR))

I’m sure the other volunteers share my sentiment that, ‘The payment is that you get to work on something that is way cool!’ On a scale of one to ten, this project was an eleven. However, it was no cake walk—it was hard work. Lou McFadin (W5DID), ARISS Hardware Manager, recalls, “Volunteers have great enthusiasm at the beginning of the project. As time goes on, people lose interest or have other obligations.”

Vibration Testing ARISSat-1 (from left to right Lou McFadin [W5DID] and Gould Smith [WA4SXM])

Volunteers did come and go. A project this large and complicated can burn people out. The project will move at its own pace. People do have a life and family. However, for the people who stuck with it, this was an incredibly satisfying experience. Here’s a great story about the camaraderie of the development team by Tony Monteiro (AA2TX), AMSAT Vice President of Engineering:

“The Software Defined Transponder (SDX) first came to life around midnight on April 4, 2009. The development work had been going on for several months, and the team had all gathered at Microchip to integrate the hardware and software for the first time. It had been a pretty intense couple of days and we were all getting a little punchy by then. We were intently focused on getting the Morse-code beacon working. This was to be the first signal generated by the SDX and, when it finally spit out absolutely perfect Morse code, we had high-fives and huge smiles all around. That is, until Lou pointed out that the perfect signal from the SDX did not sound at all like real Morse code; the kind you hear on the air. Without saying anything, I added a few more lines to the software and reloaded the SDX. When run, the Morse beacon chirped like an old WWII AN/ARC-5 tube transmitter, and the hilarious scene of grown men laughing uncontrollably and acting like a bunch of silly kids is one I will certainly never forget. Although commented out of the flight code, you can still find the few extra lines in the CW beacon source file; left there for good luck!”

Hardware went through several revisions. Three to five revisions were the rule. There was much to learn from the prototypes—especially from the hardware fit checks and interconnections. Jerry Zdenek on the camera logic:

“[It was a challenge to get] all the logic gates to fit in the CPLD. The video capture went from being a simple SPI interface to a parallel host port, and then we added image data analysis into it, too. Occasionally, it would just stop fitting for no good reason. I fought it for a while, but we ended up spinning the board to put a bigger, newer CPLD on that was a more flexible architecture.”

Each of the subsystems had a microcontroller and there was much programming—including the iterations over the serial communications links. Here is Jerry again, telling the tale of getting all the code to fit inside the 8-bit PIC16F887 microcontroller on the Power Supply Unit (PSU):

“I had to keep iterating, adding and removing code and data, and optimizing it until it worked. Debugging was fun too, because it's real-time I2C? talking to the IHU running on another processor. There was no debug serial port available on the PSU. So, until the I2C was up and running reliably enough that I could send out debug data over it, I had to use two computers and single-step each processor alternating. The USB logic analyzer would burp and lose the data stream at the worst times, too. Lots of Fun!”

The SDX subsystem, CPLD camera circuitry and the PSU subsystem were all covered in Post #5.

How was it paid for? Volunteers provided their time, work benches, and test equipment. But there are still materials to be bought and travel arrangements—airfare and hotel—for the weekend work meetings and safety reviews with NASA. The answer is much of the cost was covered by AMSAT. AMSAT is a non-profit, amateur satellite research and development organization that subsists largely on membership dues and donations. AMSAT is still taking donations for ARISSat-1 and future projects. Donations can be made from the AMSAT Web site.

Group photo from one of our weekend work meetings (from left to right, Bob Davis (KF4KSS), Jim Johns (KA0IQT), Tim Moffat, Joe Julicher (N9WXU), Larry Brown (W7LB), Phil Karn (KA9Q), Steve Bible (N7HPR), Bill Reed (NX5R), Jerry Zdenek (N9YTK), Lou McFadin (W5DID), and Tony Monteiro (AA2TX))

There you have it, a tale of challenge, intrigue and solutions. It is by no means a fairy tale. This project was hard work—all on volunteer time. And it was not free! What was the payback? The chance to work on an über cool project, work with some great engineers, learn new things, and make new friends. But most of all, to see and hear the enjoyment from people around the world working with ARISSat-1.

Next week, I’ll answer some of the most frequent and interesting questions that engineers have been asking me about this project.