Remote Access Satellite Sensor Link

Remote Access Sensor Link | Frequently Asked Questions

1. Who is providing the RASSL service?

The RASSL system is a joint venture between North Star Science and Technology, LLC, Applied Micro Design, Inc., and our client companies. Client companies currently include YSI, Inc. and Remote Data Systems, Inc. (RDS). YSI and RDS interact with clients, set up new accounts, and conduct all marketing, billing, sales, and support functions. Applied Micro Design performs all engineering functions associated with the RASSL products and services, including design and production of the RASSL terminals, as well as firmware and software programming and implementation. North Star is headquartered in Baltimore, MD, and Applied Micro Design is headquartered in Germantown, MD.
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2. What satellite system does the RASSL system operate through?

The RASSL terminals transmit through the Globalstar satellite system. Signals from the RASSL terminals are received by Globalstar's constellation of 48 Low Earth Orbiting (LEO) satellites and are relayed to ground-based gateways. From there, the data is forwarded to a www data portal (www.sensorlink.biz) for client access.
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3. Can I use the RASSL system with sensors other than those provided by YSI and RDS?

Yes, but not without some changes to the RASSL software and firmware that we would need to make. The RASSL team will interface to other sensors at our expense, so if you have a specific request please provide it to sales@sensorlink.biz.
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4. Is the RASSL system really REAL TIME?

It is "real time" in the sense that transmissions from the RASSL terminal in the field to the satellite and back to the ground occur instantaneously, and thus the resulting data can be forwarded to the www data portal for distribution shortly after receipt on the ground. However, we have set up our RASSL terminals to attempt to send each message a total of 3 times (once initially, and then 2 retries after that, with each retry scheduled 30-60 seconds after the last) to ensure that each message (i.e., each distinct sample reading) will be successfully uplinked to the satellite. Not every uplink attempt is successfully received by the satellite, and thus (in an effort to ensure that all of the required data is, in fact, transmitted and received, we scheduled the terminals to attempt each message a total of 3 times. What this means is that, for a given sample reading, if the initial uplink attempt is not successful, the sample reading could be several minutes old (roughly 2 minutes old) by the time a retry of that same message is successfully uplinked and posted to the www site. If an initial message is successfully uplinked to the satellite (i.e., on the first try), the data will be posted to the www data portal within seconds of its transmission from the terminal in the field. However, if the first uplink attempt is not successful, the message data will be a few minutes old by the time it gets through; just how old will depend on which retry attempt is the successful one. Importantly, it should be noted here that the Globalstar constellation of 48 satellites is large enough and distributed enough throughout the sky that 2-4 satellites will be in view of any RASSL terminal at any one time. And thus, there is no delay in the system due to waiting for a satellite to pass overhead of a terminal.
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5. Where can I put a RASSL terminal in the field?

The answer is virtually anywhere, with caveats. The RASSL terminal is designed to be deployed in the field in remote or difficult to access places. They can also be deployed in easy to access spots, but we believe that most deployments will occur in areas where there is little infrastructure and/or cell phone coverage. The terminals are fully waterproof and weatherproof and can be left at a deployment site for long periods of time without servicing (provided they have a sufficient power supply). However, because they transmit to a satellite system, they ideally need a clear view of the sky in order to optimally uplink their messages to the satellites. They can transmit through tree canopy cover, even wet canopy cover, but the ideal is a clear sky above the RASSL terminal. They should not be placed next to (or under) large structures, such as buildings, caves, parking garages, or metal structures (like a metal fence), etc.
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6. How much data can be transmitted through the RASSL system with each message?

The RASSL system is a databurst system. In other words, it is designed to transmit a distinct message all at once, as opposed to an open connection with the satellite. Each individual uplink message can contain up to 72 bits of data. However, we can string up to 4 separate messages together in sequence to enable the system to transmit a total of 288 bits of data at a time. These transmissions occur one after the other, so there is no waiting or latency. Importantly, even if we send 4 messages worth of data to the satellites at a time, the cost is the same to the end user. In other words, a user is not charged any more if his/her message payload is larger than 72 bits, so long as the total message payload is no larger than 288 bits.
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7. Is the RASSL system one-way or 2-way?

The RASSL system is currently configured for 1-way operation. The RASSL terminal is programmed at the lab or office to transmit according to a selected time interval (such as every 4 hours, or every 2 hours, etc.). Once it is deployed in the field, there is no way to change the transmit interval without going physically to the unit and re-programming it in the field.
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8. How do I program my RASSL terminal?

A software interface to a computer is supplied with any purchase of RASSL terminals, and this interface allows you to program the RASSL terminal to transmit as often as you wish. You can connect your RASSL terminal to a computer via an RS-232 port and set it up as you desire. Alternatively, you can have us program the terminal for you.
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9. Where is RASSL service available?

Right now, RASSL service is available throughout most of North America, the Middle East, Turkey, and all of Europe (including the UK).
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10. How do I sign up for RASSL service?

Simply contact Blake Henke at 410-961-6692 or via e-mail at sales@sensorlink.biz.
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11. How is the data supplied to a customer?

The data is supplied in the form of a viewable and downloadable Excel file on the RASSL data portal (www.sensorlink.biz). The www data portal is accessible via a client's user name and password, which is supplied with the purchase of RASSL products and services. The data can also be forwarded to a client's own www site or FTP site, or the data can could be e-mailed.
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12. What are the terms of payment?

For clients within the USA, payment is requested for the RASSL terminals at the time of delivery, net 30 days. For international clients, payment for RASSL terminals is requested in advance of delivery. Satellite airtime charges for both domestic and international clients will be billed monthly, at the end of each month, with payment requested net 30 days.
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