BALOR IRIG-B GPS Feature – FAQ

Q: How does the timestamping process work in the Balor?

Balor receives an IRIG-B signal through an SMA connector on the back plate. The IRIG-B signal is decoded by the camera firmware. The time code is received at 1 Hz. The camera samples this signal with a 100MHz clock, which allows for higher precision timing data to be derived.

Individual systems/time servers will quote an accuracy which is the time taken to receive and transmit the time signal – this is an inherent limit of the system. The Balor subsequently detects the time signal (at TTL levels) and provides sub-second information relative to the start of exposure.

Q: What timestamp accuracy does the Balor offer?

Balor offers a 10ns accuracy.

Q: Which time code formats does the Balor support?

Balor will support the B004, B005, B006 and B007 formats. These are all TTL level (unmodulated) formats (unlike B12x, for example). The last 3 of these formats include extra data that is not required to use Andor’s SDK3 function (which retrieves seconds, minutes, hours, days and years*).

*If B000 – B003 are supplied to the camera the year will not be retrievable via SDK3 command. This might not be an issue for some users, but we don’t recommend it.

Example of a GPS unit/time server (provided by Meinberg):

• GNS181 Racked GNSS receiver,
• SDU for splitting the IRIG-B signal,
• TCR180PEX-EL for synchronizing the computer time.

The IRIG-B is output from the GNSS system, and then the Meinberg SDU routes this signal (among others) to the cameras and the computer.

See also:

• Ninja-Time-Server.pdf (endruntechnologies.com)
• Welcome to Spectrum Instruments - leaders in high-performance GPS disciplined precise time and frequency references!
• bc637PCIe (GPS) | Microsemi

Please note that these are suggestions only. Andor does not provide GPS units/time servers. Please contact the corresponding supplier directly.

Q: How does it work to add timestamp information (IRIG B GPS info) to a .fits file/header in SOLIS?

When Solis generates a fits file, it checks to see if IRIG B data is available.  If it is, a separate table is added to the file, which includes the raw IRIG data for each frame in the series.

Q: What is the interface/connection between the time server and the camera / computer?

The camera has a 50Ω SMA connector on the back plate, which is the IRIG-B input.

Q: Which cable is provided by Andor?

We supply a 2 metre SMA to BNC cable for the IRIG-B. Through customer special requests, it is possible to inquire about longer cables.

Q: Is a software required to interface the Balor with the time server?

The time server is set up independently and must provide the IRIG-B signal to the camera. The Balor user must enable the metadata feature and configure the metadata to include IRIG-B data. The Andor SDK manual will provide further detail. This feature is also supported in Solis. When enabled, the camera will decode the IRIG signal and append the timecode and further time precision data to the frame data.

Q: Did Andor test different time servers / GPS units?

Unfortunately, we haven’t tested multiple receivers but a receiver which outputs IRIG-B timecodes in unmodulated (i.e. no carrier frequency, DC level shift) format at TTL voltage levels, should be compatible with the Balor.

Note: Modulated IRIG-B signal is not supported

Q: How should a GNSS antenna be place in the dome of an observatory? Can a receiver inside the dome still work?

At Andor, we had to position an antenna outside of our building, as it may not receive signal indoors. However, the GNSS system manufacturer should offer advice on antenna connections.

Q: Which other Andor cameras also offer IRIG B GPS timestamping functionality?

The IRIG-B GPS feature is available with the iKon XL 231 & 230 CCDs (note: with a different timestamp accuracy and input supported than for Balor) and, most recently, for the Marana sCMOS.