9. INTANGIBLE ASSETS AND GOODWILL

Intangible assets are as follows:


	December 31, 2018						December 31, 2017
	Gross carrying value		Accumulated amortization		Net carrying value		Gross carrying value		Accumulated amortization		Net carrying value
Customer relationships	$	619	$	(58)	$	561	$	622	$	(16)	$	606
Backlog		332		(120)		212		331		(23)		308
Technologies		330		(86)		244		477		(107)		370
Software		198		(71)		127		245		(88)		157
Image library		80		(32)		48		80		(8)		72
Trade names and other		41		(9)		32		114		(27)		87
Non-compete agreements		21		(13)		8		20		(2)		18
Total intangible assets	$	1,621	$	(389)	$	1,232	$	1,889	$	(271)	$	1,618

The Company identified triggering events for impairment during the second half of 2018 related to intangible assets of its GeoComm business, a reporting unit in the Space Systems segment. At the beginning of the year, the Company forecasted it would be awarded three to four contracts for GeoComm satellites, or approximately thirty percent of the overall 2018 industry awards. During the second half of the year, it became clear that industry and macroeconomic factors had declined substantially from earlier forecasts. Due to the decline in the GeoComm market, and the uncertainty surrounding the future of the Company’s GeoComm business, an impairment loss was recognized, primarily due to future cash flows associated with the intangible assets not being sufficient to cover the total book value of those assets. For the year ended December 31, 2018, the Company recognized impairment losses of $53 million, $47 million, $20 million and $2 million related to the technology, trade name, software, and customer relationship intangible assets of the GeoComm business, respectively.

The Company also recognized an additional $2 million of impairment losses related to software intangible assets associated with the WorldView-4 satellite.

Amortization expense related to intangible assets was $292 million, and $100 million for the years ended December 31, 2018 and 2017 respectfully. The increase is primarily due to the inclusion of a full year of expense related to the acquisition of DigitalGlobe.

The estimated annual amortization expense related to finite-lived intangible assets as of December 31, 2018, is as follows:


	Year ended December 31,
		2019		2020		2021		2022		2023		2024 and thereafter
Amortization expense	$	276	$	240	$	168	$	129	$	56	$	363

Goodwill as of December 31, 2018 is as follows:


	Space Systems		Imagery		Services		Total
Balance as of December 31, 2016	$	625	$	27	$	47	$	699
Acquisitions		143		1,400		126		1,669
Foreign currency translation		6		—		—		6
Balance as of December 31, 2017		774		1,427		173		2,374
Impairment losses		(494)		(142)		—		(636)
Goodwill on acquisition of Neptec		22		—		—		22
Disposal of immaterial subsidiary		—		—		(3)		(3)
Foreign currency translation		(6)		—		—		(6)
Balance as of December 31, 2018	$	296	$	1,285	$	170	$	1,751

Goodwill impairment

Subsequent to October 1, and before the Company had completed its annual goodwill impairment test, the Company experienced triggering events suggesting that the fair value of the Company had decreased substantially since October 1. These triggering events required an additional goodwill impairment test, which was completed as of December 31. The triggering events included a sustained decline in the Company’s stock price, further declines in the SSL GeoComm business, and the loss of the WorldView-4 satellite. The Company’s reporting units as of December 31, 2018 were comprised of: Imagery, Services, MDA, SSL GeoComm, and the remainder of SSL (“SSL Other”). MDA, SSL GeoComm and SSL Other are reporting units in the Space Systems segment. The Company estimated the fair value of each reporting unit using an income approach. The income approach utilizes a discounted cash flow approach, which requires the use of significant judgments and estimates, including future cash flows, terminal growth rates, and discount rates. The Company evaluated the aggregate fair value of its reporting units against market data to support its fair value estimates. The Company determined that goodwill was impaired as of December 31, 2018 for its MDA, Imagery and SSL Other reporting units and recorded non-cash impairment charges of $477 million, $142 million and $17 million, respectively.