Glossary
Ancillary Data ·
Command ·
Command History Data ·
Committed Information Rate (CIR) ·
Critical ·
Increment
Integrated Planning System (IPS) ·
Non-critical Highly Desirable ·
Non-critical Routine ·
Operations Data
Payload Ground Ancillary Data ·
Payload Health & Status ·
Payload Systems Data ·
Performance Categories
Real-time (RT) Payload Data ·
Voice Over Internet Protocol ·
VPN
Ancillary Data:
Ancillary data is a selected subset of core systems data and other onboard generated
data (including payload generated data) required by users to supplement data
for payload data analysis. This data is necessary for executing real-time operations
and for analysis of payloads by ground controllers as required. It contains state
vectors, spacecraft attitude data, etc. Ancillary data describes the flight environment
in which the payload is operated. Back
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Command
Standard Command - maximum of sixty-four 16-bit words consisting of three word
Consultative Committee for Space Data Systems (CCSDS) primary header, five word
CCSDS secondary header, two word Legal Station Mode indicators, up to fifty-three
actual command words, fill words - used only with ground-generated commands [the
Assembly Contingency Baseband Signal Processor (ACBSP) requires twenty-four word
minimum commands], and one Add without Carry Checksum word.
Data Load Command - maximum of two hundred eighty-eight 16-bit words consisting
of three word CCSDS primary header, five word CCSDS secondary header, five words
of address and valid station mode information, up to two hundred seventy-four
actual data words, and one Add without Carry Checksum word.
Payload Commands - reference above command definitions as applicable to payloads. Back
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Command History Data:
The command history shows the execution status of the commands issued from the
ground or by the crew and the commands automatically executed on board. It includes
the following items:
a) Command name and type
b) Issuer and addresses
c) Issuance time and execution time
d) Reception approval and rejection
e) Execution results
f) Other Back to Top
Committed Information Rate (CIR)
The amount of network bandwidth guaranteed to be available for a particular WAN
service. When a particular source of data bursts above the CIR for that service,
service availability is only guaranteed for the CIR.
Critical
An availability category, which includes any ground support function, required
to assure safety of the crew and survival of the ISS. It also includes data,
which, if unavailable, could cause irreparable damage, including possible loss
of the crew, the station, or the associated capability to process vital data.
Services classified as critical require immediate restoration in the event of
a failure. Back to Top
Increment
During ISS assembly phase, the time period between the launch of a particular
crew the undocking from the ISS of the return vehicle for that crew. Back
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Integrated Planning System (IPS)
IPS is a collection of computer-based tools used for flight planning. These include
trajectory analysis, mission planning, robotics analysis and planning, shuttle
ascent and descent, resource analysis, and direct mission support for near real-time
planning and analysis. The IPS ground communications requirements will be derived
as file transfer requirements. Back
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Non-critical Highly Desirable
An availability category, in which restoral of failed services classified as
Highly Desirable may be accomplished within 2 hours without creating a hazardous
condition to the ISS or USGS. Back to
Top
Non-critical Routine
An availability category, in which restoral of services classified as Routine
may be accomplished within 24 hours without creating a hazardous condition to
the ISS or USGS. Back to Top
Operations Data
Essential and extended telemetry data describing the status of onboard systems
necessary for successful mission operations and the crew’s health and safety
is known as Operations Data. This data is contained in the Command and Control
(C&C) Multiplexer/Demultiplexer (MDM) Current Value Table (CVT) and downlinked
in the S-Band telemetry. Also referred to as “core systems” data. Back
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Payload Ground Ancillary Data
Payload Ground Ancillary Data includes data not available in the Ku-Band downlink.
This data includes core systems data not downlinked as Payload Flight Ancillary
Data, POIC computations data, STS data required during ISS related shuttle operations,
and other data available through the HOSC but not contained in other ISS telemetry
streams. This data supplements (not duplicates) other ISS telemetry sources and
is required for successful payload operation and data analysis. Back
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Payload Health & Status
Payload H&S data consists of sensor data of payloads and equipment in the experiment
racks and status data of payloads and racks output by the control equipment.
This data does not include science data. Payload H&S data is a subset of payload
data required by the ground/Payload Operations Integration Center (POIC) to monitor
payload conditions onboard the station. It will be rack level and payload level
data and can include elements of ancillary and safety data. This data is downlinked
via S-band.
The following description of POIC H&S downlink is extracted in whole from the
Payload Systems Development Handbook, D683-70830-1 Revision A:
The content of the POIC H&S downlink is specified in part by the Payload Executive
Processor (PEP) Status Definition Table. The PEP Status Definition Table contains
up to 1 Kbytes of CVT data. The remaining portion of the POIC H&S data consists
of payload H&S data.
The data that is downlinked via Ku-band from this service typically includes
but is not limited to the following data items:
a) Payload Executive Software (PES) History Log - data collected on processing
of PES.
b) PES Service Status Data - data on current state of services provided to payloads.
c) PES Mode - current PES system mode.
d) Core Systems Data - various elements of core systems data required by the
ground.
e) Payload Health & Status data - includes elements of ancillary data and safety
data.
f) Automated Payload Switch (APS) Status data
g) Payload Ethernet Hub/Gateway (PEHG) Status data.
Back to Top
Payload Systems Data
Health and Status information from the experiment equipment is a subset of Payload
Systems data. Payload Systems data includes normal hardware and software configurations
and status telemetry. Payload systems data includes that data pertaining to payload
support systems (PEHG configuration, APS status, etc.) that will allow the ground
to monitor the systems. This data is downlinked via Ku-band. Back
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Performance Categories:
The NISN has defined four service performance categories for IP routed data services.
Those definitions and accompanying table, extracted from the NISN Services Document
(February 1998 version) in whole, are included below.
1. Real-time Critical Service - A Real-time Critical Service is characterized
by very high service availability and, in the event of failures, extremely short
restoral times (measured in seconds vs. minutes). Representative applications
include spacecraft launch commands and telemetry and real-time ground equipment
configuration messages. Provisioning this service normally entails redundant
equipment, dedicated bandwidth, and/or the geographically diverse routing of
circuits. Security may be achieved through physical isolation of network resources,
route filtering, traffic filtering, and/or the application of firewalls as indicated
by customer requirements.
2. Mission Critical Service - A Mission Critical Service is characterized by
high service availability and, in the event of failures, brief restoral times
(measured in minutes vs. hours). Representative applications include spacecraft
commands, housekeeping, and unprocessed instrument data as well as real-time
ground equipment configuration messages. Provisioning this service may require
redundant equipment, dedicated bandwidth, and/or the geographically diverse routing
of circuits. Security may be achieved through physical isolation of network resources,
route filtering, traffic filtering, and/or the application of firewalls as indicated
by customer requirements. Mission critical data is routed over FTS2000 dedicated
circuits. TCP/IP, UDP/IP and, in special cases, Serial Clock and Data are the
protocols that are supported on the mission critical network.
3. Premium Service - A Premium Service is suitable for applications that require
short and predictable round-trip times. Provisioning a Premium Service may require
dedicated, under subscribed, or priority access to bandwidth. The Premium Service
is engineered according to peak traffic requirements. Users of the Premium Service
can anticipate the ability to burst traffic considerably beyond their documented
requirement. The Premium Service network backbone consists of commercial carrier
ATM circuits. FTS2000 dedicated circuits are in place to provide backup connectivity.
Customers will be charged a fixed amount per kilobit of bandwidth required. This
Premium Service charge will be higher than the Standard Service charge. Customers
will be notified in advance of scheduled maintenance outages. The Premium Network
is monitored 24 hours a day by a network management center.
4. Standard Service - A Standard Service is suitable for applications that can
tolerate some probability of congestion and varying, but bounded, delay. These
applications include built-in recovery mechanisms (e.g., TCP) for congestion
or packet loss events. Examples include bulk data transfer, E-mail, and web browsing.
Although these applications may better tolerate variations in network performance,
network sizing is critical to providing a reliable and usable service to NISN’s
customers. NISN will establish utilization thresholds which, when exceeded, will
require NISN to install more capacity to maintain performance levels. For example,
when average link utilization during the busy hour exceeds 75% for a Standard
Service, NISN will initiate action to increase the link capacity. Note: All non-IP
protocols will be treated as having standard performance requirements.
The Standard network capacity is engineered to meet actual usage levels, ascertained
through a collection of network statistics. Users of the Standard Service will
experience a service consistent with their sustained bandwidth requirements and
should not expect the network to accommodate bursts beyond their documented requirement.
The standard service network backbone consists of commercial carrier ATM circuits.
Customers will be charged a fixed amount per kilobit for their required bandwidth.
The Standard Service charge will be lower than the Premium Service charge. Customers
will be notified in advance of scheduled maintenance outages. Standard Service
is monitored 24 hours a day in the network by a Network Operations Center. Back
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Real-time (RT) Payload Data
Actual experiment data from the payloads is data collected by the instrument.
Also referred to as Science data. Downlinked via Ku-band.
Systems Health & Status (H&S) data
System H&S data, a subset of operations data, consists of sensor data of core
systems and status data of control equipment. Back
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Voice Over Internet Protocol
Voice over Internet Protocol (VoIP) is a means of providing extension of Mission
voice conference nets to desktop workstations via common IP based networks. Audio
is transmitted as User Datagram Protocol (UDP) and is accessed through a Web
browser interface. Packets can also be encrypted and encapsulated for enhanced
security. Back to Top
VPN
VPN (Virtual Private Network), is the use of encryption in the lower protocol
layers to provide a secure connection through an otherwise insecure network,
typically the Internet. VPNs are generally cheaper than real private networks
using private lines but rely on having the same encryption system at both ends.
The encryption may be performed by firewall software or possibly by routers.
Link-level (layer 2 and 3) encryption provides extra protection by encrypting
all of each datagram except the link-level information. This prevents a listener
from obtaining information about network structure. While link-level encryption
prevents traffic analysis (a form of attack), it must encrypt/decrypt on every
hop and every path.
Protocol-level encryption (layer 3 and 4) encryption encrypts protocol data but
leaves protocol and link headers clear. While protocol-level encryption requires
you to encrypt/decrypt data only once, and it encrypts/decrypts only those sessions
that need it, headers are sent as clear text, allowing traffic analysis.
Application (layer 5 up) encryption is based on a particular application and
requires that the application be modified to incorporate encryption. Back
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