ISS Crew Contact Part 1 – Ground Station Design and Construction

Satellite 3.0 Station Control Details
Ground Station for Satellites and the ISS

Our planned ISS Crew Contact is almost here! It will take place sometime during the first week of December (December 3rd – 8th) at the Hudson Memorial School (HMS) here in Hudson, NH. I am planning a series of articles here on our blog to explain the process for preparing our ground station(s) and making our contact.

The Beginning

Dan Pooler, AC1EN who is a teacher at HMS began this process almost a year ago by reaching out to the Nashua Area Radio Society. Dan wanted to do an ISS Crew Contact at his school and asked if we would help him with the Amateur Radio elements.

We decided early on that we wanted a Direct contact (one which uses an on-site Amateur Radio Ground Station).

ARRIS Ground Station Recommendations

The first thing we did was to look at the ARISS Ground Station requirements document. We learned that we needed to build two Ground Stations – a Primary Station and a Backup Station. These requirements and our interest in Satellite Communications led to the construction of a series of Portable Space Ground Stations.

The Primary Station

The primary station requirements are as follows:

  • Transceiver with 50–100 W output, 1 kHz tuning steps, and 21 memories capable of storing split frequencies
  • Low-loss coax (such as 9913 or LMR-400)
  • Mast mounted receive pre-amplifier
  • 14 element yagi antenna with switchable circular polarity
  • Antenna rotators for azimuth (0–360°) and elevation (0–180°), with an interface for computer control
  • Computer running tracking software for antenna control (including flip mode operation)

The ARISS approach is to used a series of “secret” uplink frequencies which are determined and provided only to the contact operators before each contact. Doppler correction is not required on the 2m band where the crew contacts take place.

Our Portable 2.0 Satellite Station already existed, and it met many of these requirements with a notable exception:

14 element yagi antenna with switchable circular polarity

Satellite Antenna Details
Satellite Station 2.0 Antenna Details

Our 2.0 Station has an 8 element yagi with fixed polarity. This requirement turned out to have a much more significant impact on the design of the Primary Ground Station than just changing the antenna and ultimately led to the construction of our Portable Satellite Station 3.0. More on this in a minute…

The Backup Station

The backup station requirements are as follows:

  • Transceiver with 50–100 W output, 1 kHz tuning steps, and 21 memories capable of storing split frequencies
  • Power amplifier with 100–200W output (optional)
  • Low-loss coax
  • Mast mounted receive pre-amplifier
  • Omnidirectional antenna, either vertical (preferred) or eggbeater style
  • Uninterruptible power source (UPS or battery)

Our Approach

After consulting with the ARISS folks and some thought, we decided to use the then current Satellite Station 2.0 as the Backup Station and build a new Satellite Station 3.0 for use as the Primary Station. This approach also involved installing a larger rotator to accommodate the larger antenna and a heavier fiberglass cross-boom. The 3.0 station would also receive a more capable antenna for the 70 cm band and add a 23 cm antenna for a third band.

The plan included upgrading the 2.0 Station Antennas to include switchable polarity and the addition of a 200W power amplifier for 2 m to compensate for the reduced gain of the smaller 8 element yagi in the 2.0 station.

Building The Primary Station

Satellite Station 3.0 Antenna System
Satellite Station 3.0 Antenna System

The construction and testing of the 3.0 Station are well covered in articles on our Blog so I’ll just share a little information about the final result. The new antenna system used the same ground-based roof tower arrangement that worked so well for the 2.0 station. The larger 3.0 antennas are center mounted on a fiberglass cross boom to prevent the boom from affecting the antenna patterns. We’ve also added a 23 cm loop yagi for a third band. The 3.0 antenna system also uses a more powerful Azimuth-Elevation Rotator from Alfa-Spid.

2m Yagi Switchable Polarity Feedpoint
2m Yagi Switchable Polarity Feedpoint

The new 2 m and 70 cm antennas use relays at their feed point to enable remote switching of the antenna’s polarity between Left-Hand and Right-Hand circular polarity.

Satellite 3.0 Station Radio and Controls
Satellite 3.0 Station Radio and Controls

The upgraded 3.0 ground station adds a control console for switch the polarity of the antennas and a custom built PPT Router Device to manage PTT sequencing of the radio and the pre-amplifiers at the antennas.

Computer Control via MacDoppler
Computer Control via MacDoppler

We continue to use the excellent MacDoppler software to control tracking and Doppler correction in the 3.0 Station.

Building The Backup Station

Upgraded 2.0 Antennas
Upgraded 2.0 Antennas

The upgrades to the 2.0 Antenna System involved the installation of Polarity Switching relays in the feedpoints of the 2.0 antennas. This upgrade was a fairly straightford one.

Backup Station Radio and Controls Test
Backup Station Radio and Controls Test

The ground station side was more involved as we needed to build a complete, second station. I was able to purchase an Icom IC-910H radio used in good condition for this purpose. The rest of the station components were similar to the Primary Station.

Backup Station Test at the Fall Tech Class
Backup Station Test at the Fall Tech Class

We tested the Backup Station at our Fall Technician License Class and it worked great! several of our class students used the station to make their first satellite contacts.

I am currently working on adding the 2 m amplifier and improving the PTT sequencing system on the Backup Station and I plan to post more about these upgrades in here in the near future.

Audio System for Our Contact

Mixing Board at HMS
Mixing Board at HMS

Our contact will take place in the auditorium at HMS. The room has a high-quality sound system and mixing board for audio.

Audio System for ISS Contact
Audio System for ISS Contact

Dave, K1DLM is part of our ISS Crew Contact Team, and he has quite a bit of pro-level audio experience. He has put together the following plan for our Audio System. His design allows us to smoothly transfer audio to and from either the Primary or the Back Stations. We are also planning to record video and Livestream video to the N1FD Facebook page during our contact, and his design supports these elements as well.

Data System for ISS Contact
Data System for ISS Contact

The final element in our plan is the Data System. The network at HMS is very tightly controlled from a security point of view and this makes it difficult to use for contact critical functions like access to up to date Keplerian Elements for our straightforward. Dave has an LTE-based Internet Access System that we have used in the past and we’ve elected to use this to support our stations. We are planning to use the HMS network to transport the Livestream video from our contact. We’ll be using a Mevo Internet Camera for this purpose.

A Million Details…

As you can probably imagine, there a many details that go into making a project like this possible. Here’s a rough timeline of some of the major remaining steps from a Ground Station point of view:

  • Assemble both stations at our QTH with the 2m amplifier and the final 215′ control cables and feed lines – In progress, should be complete in a few days.
  • Full Station Test – add the Audio and Data System components and test the full station at our QTH – Within a week.
  • Configure and Test Data Network Access – for Live Streaming Video and computers and HMS.
  • Setup Ground Station at HMS and perform Dry Run Test – Complete by December 1st.

Dan and the HMS faculty team are also very busy finalizing the student’s questions and handle press related activities.

We hope our readers will join us via the Livestream video for our contact. We’ll post more on this as we get closer to our contact!

Fred, AB1OC

2 thoughts on “ISS Crew Contact Part 1 – Ground Station Design and Construction

  1. THANKS very much for your well documented efforts. Inspired by your designs, I have begun construction of a ground station based on your 2.0 system. Eric K7EAS

    • Thank you Eric. You’re welcome to post comments here if you have questions as you go. I’ll be glad to try to help.

      – Fred, AB1OC

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