This week was very successful on the programmatically part of the mission. We finally received approval from ARISS TE&S (Amateur Radio on the ISS Technical Evaluation & Support) to use the antenna and to get support for the operations. Additionally, on our way through the ESA safety process we completed Phase II.
As we want to use ARISS antennas aboard the ISS, we need ARISS approval and support. ARISS has been included in our experiment plans early in the process, but there is a lot to examine and discuss during the development. First, safety of astronauts and spacecraft is the most important issue. Since we want to use antennas that transmit up to 50W during ARISS operations, we have to make sure that our system, that is integrated in the existing setup, does not cause problems. Although no hazard for astronauts is likely, a wrong setup might lead to unintentional reflection of RF signals that could damage the ARISS equipment. For this reason, the MarconISSta equipment had to be carefully examined. With the help of ARISS TE&S members (Oliver Amend, Lou McFadin, Ciaran Morgan, Frank Bauer to name a few), we adapted our setup such that it cannot harm ARISS equipment. The setup can be seen in the figure below.
All new items are colored blue. Our receiver (LimeSDR) can use the VHF/UHF and L/S antennas. For the use of L/S band, there is a free antenna and we only need to design an adapter. To include our receiver in the VHF/UHF setup, we make use of an RF coupler. This device feeds through all signals from and to ARISS transceivers (with low loss of about 0.3 dB). The coupled ports of the coupler are connected to our receiver and we can record data, even without switching between our system and ARISS systems. This does not only make operations more safe (no “wrong” switch position can occur), but also safes crew time for the switching procedure. The daily plan of an astronaut is split into 5 minutes activities. Even if we only want to switch from our system to ARISS, which would talke 1 second, it would talke 5 minutes of the astronaut schedule and therefore waste a lot of time. Accordingly, the RF coupler is much better than the switch and a real improvement to the system. Thanks Lou McFadin to come up with this idea! The Astro Pi will process and store the experiment data and we will downlink the data via Station LAN. As you can see, the complete setup runs automatically. We do not have to coordinate with ARISS school contacts or other activities which makes the integration into the complex schedules much easier. With this setup, ARISS is in full support for the project, as long as we complete the safety review process.
Safety review is mandatory to get your system to the ISS. Review items are structural, electrical, biochemical and many more.
- Does the system have sharp edges that could hurt the astronaut?
- Can the system break during launch?
- Does the system get to warm for touching during operations?
- Does the system contain batteries?
- Can over-/under-voltage occur?
- Does the system produce or malfunction due to electromagnetic fields?
The ESA safety review panel (ESRP) looks into all these issues in four phases (Phase 0,I,II,III). The payload developer (we) needs to proof that none of the items is an issue. On our way through the process, we already did touch temperature tests, vibration tests, visual inspection for sharp edges, functional tests etc. With that, we passed the Phase II Flight Safety Review this Tuesday and are already preparing for the Phase III Flight Safety Review in the end of January. Before that, we have a lot to do:
- EMC testing
- USB interface testing
- Finalization of hardware setup and operations schedule
- Release of software.
But we are positive that we can still hold our self-set deadline for delivery (end of January 2018). With that, we will probably use either Orbital Cygnus or SpaceX Dragon to send our system to the ISS some time between May and July 2018.
For now, we wish everybody merry Christmas, a happy new year and lots of success for 2018. Thank you to DLR, ESA, NASA, ARISS for the support! Also, thank you to all the students who participate in this project on a voluntary basis, besides their well-filled study program!