by February 6, 2003 0 comments



The Hubble Space Telescope (HST) is a large optical telescope. It orbits the earth and takes detailed pictures of stars, galaxies and solar-system objects…whatever is out there. 

The HST uses an elaborate spacecraft-management system to keep it afloat and working. In this respect, it is no different from other spacecraft. The main elements of the system are the Computer Support System Module and the Advanced Tracking and Data Relay Satellite (TDRS) series. The Computer Support System Module contains devices and systems needed to operate the Hubble telescope. This serves as the master control
for communications, navigation, power management, etc. The TDRS series accepts Hubble’s information for relay to the ground controllers at the Space Telescope Operations Control Center (STOCC) in Greenbelt, Maryland, US. Similarly, the TDRS also provides high bandwidth communication support
to the International Space Station (ISS) and some other satellites up there. 

7000 variables of real-time information from the Hubble telescope are transmitted to the geo-synchronous Tracking and Data Relay Satellite System (TDRSS), from which they are downlinked to the ground station at White Sands, New Mexico, and then relayed to the Goddard Space Flight Center in Maryland using what is known as the Control Center System (CCS).

Further data analysis is done using the Space Telescope Science Data Analysis System
(STSDAS). 

The CCS front-end uses Java applets that let engineers control and monitor Hubble from the earth. The CCS user interface has two parts: the first is control, where the telescope can be commanded to select new targets; and the second is data visualization, where the user can view telemetry and engineering data either archived or being streamed down in real time from the spacecraft. 

The CCS applets establish a direct network connection to a NASA host, where a middleware server connects to the existing server system. This allows anyone with access privileges on the Internet to view the engineering data that is being continuously transmitted by the spacecraft, and even to obtain a personalized, configurable view of this data. 

The server-side code is written in C++. 

The CCS is used to handle communication between Hubble and the ground stations for spacecraft commanding and health and safety analysis. The architecture for this is a typical secure network. 

The data sent from the telescope is analyzed using the STSDAS, which is a powerful set of tools that support software used to calibrate and analyze data. A companion package, TABLES, is a set of tools for creating and manipulating tabular data, reading and writing Flexible Image Transport System (FITS)–the widest used data format used for astronomical images–images and tables, and creating customized graphics. STSDAS and TABLES are layered on the Image Reduction and Analysis Facility (IRAF) software from the National Optical Astronomy Observatories. STSDAS and TABLES run in tandem with
IRAF.

The Space Telescope Engineering Data Store (STEDS) is intended to serve as a common data source for all the telemetry data for all the Hubble subsystems. Its design uses a typical middleware-enabled three-tier model, and it is platform-independent, as it has to be accessed over the Internet. The telemetry data stream from Hubble is transferred to the Front End Processor (FEP) via Nascom (NASA Communications Network). FEP provides a communication interface between the vehicle and ground control and captures all the downlinked data. It then forwards it to the attached All Points Archive, which interacts with the Web server to produce a Web-browser output for a client machine, and through the middleware C++ server to process the Applet GUIs.

Shruti Pareek

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